The Giovanni images shown here are generated by members of the worldwide Giovanni user community or by the GES DISC staff. The images are posted here for examination and discussion. Members of the Giovanni Facebook group can discuss these images; anyone can send images and figures to the page editor for posting here.
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MODIS Aerosol Optical Depth, April 15, 2010, showing the elevated AOD associated with the eruption of Eyjafallajökull volcano in Iceland. The direction of the ash plume toward Europe resulted in the closure of European airspace and disruption of air travel around the world.
Giovanni custom palette image of the Tennessee flooding rains, May 1-2, 2010
Earth Observatory posted an article about this tragic and massive flooding event:
Heavy Rains in Kentucky and Tennessee (their image was for May 1-3)
So I decided to see what I could do in Giovanni with a customized palette. I used the Ocean palette. I thought this provided a good perspective on the size of the system, with the red borders showing how large the system was, and the light blue giving a good indication of where the heaviest rain was. I looked at just May 1-2.
Animated GIF of MODIS aerosol optical depth over Iceland and northwestern Europe, showing the area potentially influenced by volcanic ash erupted from Eyjafjallajokull
This animation was constructed by averaging daily MODIS AOD data for four 4-week periods, starting on April 14, 2010. The maximum data value for the palette was reduced from the default of 0.9 to 0.75, to provide more emphasis to the elevated AOD areas. An online site (gickr.com) that enables creation of animated GIFs was used to stitch them together. By averaging the MODIS data over a week, it eliminates much of the data gaps that appear in daily images.
Ozone Measuring Instrument (OMI) Erythemal Daily Dose for May 25, 2009 (Memorial Day 2009)
Erythemal Daily Dose is the diurnally integrated amount of harmful UV radiation on the Earth's surface. The daily dose of the UV Record service, given in units of Joules per square meter units, is an estimate of the erythemally weighted daily dose taking into account the attenuating effect of clouds. Additionally, the estimate is corrected for strongly absorbing aerosols in the clear-sky case. This plot shows Erythemal Daily Dose for May 25, 2009, which was Memorial Day in the United States, traditionally a day with lots of outdoor activities in the spring sunshine. Surprising "hotspots" were Denver and the Grand Tetons region of Wyoming, perhaps due to clear mountain air that day.
Warm April Temperatures contribute to record low snow cover in North America
NASA Earth Observatory had an article about the record low snow cover in North America in April:
Record Low April Snow
The article accompanying the "Image of the Day" of North American snow cover said the following:
"According to NOAA, “Across North America, snow cover for April 2010 was 2.2 million square kilometers below average—the lowest April snow cover extent since satellite records began in 1967 and the largest negative anomaly to occur in the 521 months that satellite measurements are available.” Unusual warmth descended on North America in April, leading to both low snowfall amounts and rapid melt of existing snow."
As of May, Giovanni doesn't have any snow cover products available yet; they should be in MERRA and GLDAS eventually. So the image below was generated from NEESPI Daily. It is an image of AIRS daily surface temperatures (ascending), averaged for April 2010, over North America. (Units are degrees K; 260 K is -13° C or 8.6° F; 288 K is 14.85° C or 58.7° F) The area of warm temperatures in the Canadian Great Plains corresponds almost exactly to an area of zero snow cover in the Earth Observatory Image of the Day.
Tropical Cyclone Phet – a little friendly comparison/competition with NASA Earth Observatory
The NASA Earth Observatory Image of the Day on June 8, 2010 was a visualization of the precipitation and storm track of Tropical Cyclone Phet, which arose in the Arabian Sea and hit the easternmost coast of Oman, causing damage and fatalities, in the first few days of June 2010.
Because we have the same data set in Giovanni that was used by the Earth Observatory – the TRMM Multi-Satellite Precipitation Analysis Near-Real-Time Monitoring product – I decided to see if I could come up with a visualization of Phet's rainfall to compare with (and maybe have a larger WOW! factor than) the Earth Observatory visualization.
My results are below. On top, the Purple-Red-Stripes palette was used. This palette gives a nice contour effect. In the middle, the Ocean palette was used, which also has a contour effect and which brings out areas of lighter rainfall. At the bottom. the BLUE-RED (not the blue-red) palette was used. The upper bound value for rainfall was adjusted downward slightly for all of these images. See my additional comments below the third image.
I thought this last image was quite striking, but with one problem -- the black coastline outlines disappear into the black background, and Giovanni doesn't have the capability of changing the color of the coastlines (which might be a good option to add, if we had a lot more time, staff, and money). But then I remembered that I could export the KMZ file version of this image to Google Earth, which has yellow coastlines as well as land surface imagery. So that's what I did; and I think the result was pretty good. The only thing I don't know is how to get rid of the strange red "X".
Looking for the Deep Horizon Oil Spill in Giovanni's SeaWiFS ocean color radiometry data
The intense interest in the Deep Horizon catastrophic oil spill in the Gulf of Mexico has generated interest regarding whether or not the ocean color radiometry data products acquired from the Ocean Biology Processing Group (OBPG) can be used to detect it. The data products from the OBPG in Giovanni are monthly products; thus, they are averaged over the entire month. The daily imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua has observed the oil spill in the "sun glint" regions of the MODIS scanning swath, where the oil spill affects the reflection of light from the ocean surface in the area where sunlight is directly reflected back to the instrument. In ocean color radiometry data, the sun glint area is masked out, because the direct reflection area does not provide useful data -- ocean color radiometry uses light that has been absorbed and scattered below the surface, not at the surface. Because MODIS looks directly down (nadir observations) from the satellite, its data will have a broad sun glint area.
In contrast, the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) can tilt, which means that by making observations at an angle, it collects light that is not reflected directly back upward to the instrument. Thus, it can observe the area that for MODIS is affected by sun glint. Chlorophyll concentrations due to absorption by chlorophyll in phytoplankton are determined by ratios of light intensity for the different observational bands in the instrument because light on the blue side of the visible spectrum is preferentially absorbed by chlorophyll. On the red side of the spectrum, the light is only reflected by whatever is in the water; this means that the bands on the red side, particularly the band at 555 nm, is good for detecting non-absorbing substances and particles.
We worked with Stan Terzopolos, Coordinator for the Eastern Region of the Pennsylvania PIMS, Partners in Mathematics and Science Program (who accompanied Pennsylvania teachers visiting Goddard Space Flight Center to a "hands-on" training session), to see if there was any detectable signal of the Deep Horizon oil spill in the ocean color radiometry data in Giovanni. Chlorophyll did not show an apparent signal; examination of the new Colored Dissolved Organic Matter (CDOM) product seemed promising, but the data are too diffuse to show an obvious signal from the oil-affected waters. So we also examined the remote sensing reflectance at 555 nm data (Rrs555).
This data shows an interesting distribution in June 2010. Comparing to the MODIS images, the regions with elevated Rrs555 in in June appear to correspond to the general pattern that is seen in MODIS pictures from May and June. We know, however, that oil is a very dark, non-reflective substance. So is this a signature of oil -- and why is it much more evident in June than in May? What could be occurring is that as the oil "ages", it becomes lighter in color, and this lighter-colored oil (media pictures show that it is orange-ish) may reflect sufficient light on the red side of the visible spectrum to be observed in the SeaWiFS data. The June image suggests that the Rrs555 data is detecting some of the Deep Horizon oil in the Gulf of Mexico.
Below are two MODIS images from May 24, 2010 and June 25, 2010, and two SeaWiFS Rrs555 images for May and June 2010.
(above) MODIS image of the Gulf of Mexico, Mississippi Delta region, May 24, 2010, showing the reflection of the oil from the Deep Horizon oil spill in the MODIS sun glint region.
(above) MODIS image of the Gulf of Mexico, Mississippi Delta region, June 25, 2010, showing the reflection of the oil from the Deep Horizon oil spill in the MODIS sun glint region. Labels show the location of Mobile, Alabama, and the approximate location of the Deep Horizon oil rig.
(above) SeaWiFS Rrs555 image for May 2010 of the Gulf of Mexico - Mississippi Delta region.
(above) SeaWiFS Rrs555 image for May 2010 of the Gulf of Mexico - Mississippi Delta region.
Reproducing TerraDaily image of exported pollution over the Pacific
In an article on TerraDaily, "Black Carbon Implicated in Global Warming", the file MODIS image accompanying the story looked a lot like a Giovanni plot (though it isn't; it was likely created with IDL). It was fairly easy to generate the same regional plot with the Giovanni MODIS Monthly interface (shown below); the palette maximum was adjusted slightly so that it would look more like the file image in the article. The article summarizes the results of a paper published in Nature Geoscience, "Warming influenced by the ratio of black carbon to sulphate and the black-carbon source", by Ramana et al. – the second author is the esteemed V. "Ram" Ramanathan of Scripps Institution of Oceanography. In the paper, the authors indicate that the most net warming from the emissions occurs when the black carbon-to-sulphate ratio is high, and that emissions strategies intended to help reduce global warming should seek to both reduce black carbon and the black carbon-to-sulphate ratio. (By the way, this is a MODIS Terra image reproducing the TerraDaily image, and we also have MODIS Daily data from Terra. How confusing!)
North American CO2 concentrations in July from AIRS
At the recent Earth System Science Education Alliance (ESSEA) annual conference in Ithaca, NY, a session with education module developers included an examination of the Atmospheric Infrared Sounder (AIRS) carbon dioxide (CO2) data product over a spatial region – which was not something we had seen before. Paul Adams of Ft. Hays State University in Hays, Kansas, led the discussion and examination of the data. This discussion induced the generation of the Giovanni visualizations that are shown below, and provided several "revelations" about the data, the dynamics of CO2 in Earth's atmosphere, and even the Giovanni system itself.
The first visualization created was the AIRS CO2 data product over the United States (and adjacent North American regions) in July 2005, which is the third image in the sequence below. This image (once we figured out how to interpret it), showed some interesting patterns. Over forested areas (such as the Pacific Northwest and northern Rocky Mountains, the central Great Lakes region, the U.S. Northeast, and most of Canada), CO2 concentrations were low, indicating continuing uptake by plants, mostly info forests. In contrast, in the Great Plains and desert Southwest, CO2 concentrations were higher, indicating less uptake by plants – the growing season in the agricultural fields of the Midwest is nearly over in the warm days of July. The data have remarkably good spatial resolution.
Following the meeting, plots of CO2 for each July (2003 - 2010) were created. Initially, it was thought this would be easy for Giovanni, by just changing the "Begin Year" and "End Year" fields to generate a plot for July of each year. But the plot colors kept changing, so the pattern seen in 2005 wasn't as obvious in other years.
The reason for this is the way that Giovanni generated the color plots. The default color palette option is a "dynamic" scale, depending on the range of data values. Because the mininum and maximum range was different each year, the plots didn't look the same. So a standard customized palette was substituted. But when the years changed, the appearance of the plot changed, too. The reason this time was that atmospheric CO2 concentrations are increasing, so a color palette range that worked for July 2003 didn't cover the same range of data values for July 2009.
In order to portray each successive July with approximately the same color palette range, the range of minimum and maximum values had to be adjusted upward (a "moving window"). The range was usually 5-6 ppm. In the plots below, the range is shown above the plot. For July 2003, the range is 373-379 ppm; for July 2010, the range is 389-393 ppm.
One of the capabilities that would be a desirable addition to Giovanni is making an average of a data product for a given time period (usually a month) over several successive years – in essence, a climatology for that time period, if the period of time over which the data are averaged is long enough. This example, however, shows that one of the assumptions of this process would be a flat baseline, i.e., the data would fall in about the same range of values, year after year. In the case of atmospheric CO2, that isn't possible, because the atmospheric concentration is increasing every year. The annual change (a "sloped" baseline) would have to be subtracted out to provide a depiction of the variability of CO2 concentrations over North America (or another region) over several years in July, or a different month, or a season.
In the images below, one of the striking differences was in July 2009. The summer of 2009 in the eastern part of the United States was cooler and wetter than normal; this appears to have enabled more growth in the western Great Lakes states (Indiana, Ohio. Pennsylvania) and particularly in eastern Canada. Homeowners know that a summer alternating rain with cool sunny days means a lot more lawn-mowing, because the grass keeps growing. It appears that the forests and crops kept growing in 2009, too.
Another possible way to depict this would be to animate the GIF images, using a standard range (such as 5 ppm) but it might take awhile to optimize the "moving window" for each plot so that they look as similar as possible. Any takers for this challenge in the user community?
Tropical Storm Hermine demonstrates how tropical systems help offset late-summer and fall precipitation minima
As is often the case, the wonderful late summer and autumn weather in much of the United States (especially on the East Coast) has an underlying downside – low rainfall and drought conditions. That's happening again this September. One major way that these conditions are somewhat alleviated is when a hurricane or tropical storm comes inland. Usually hurricanes and tropical storms are not welcome on the coast, but their rainfall amounts (provided they aren't too excessive) can be beneficial.
Tropical Storm Hermine illustrates this point. The rain from Hermine covered a broad area from Texas all the way to Illinois, as shown in the TRMM rain track plot below. (Note: this plot was generated with our 2nd-generation Giovanni, as our hardware maintenance activities have affected data update on other Giovanni machines.)
NASA Earth Observatory showed the rain track from Hermine from September 2-8, but the remnants of the storm provided significant rain to Missouri and Illinois as well. The image below shows the rain track from September 2 through September 13.
Tropical Storm Tomas raining harder on Jamaican and Dominican Republic in the early morning of November 5
While concerns are highest for the poverty- and earthquake-stricken country of Haiti as Hurricane Tomas passes over, in the early morning of November 5, Tomas was bringing heavy rain to Jamaica and the Dominican Republic. Intense rainfall from the center of the storm was over the eastern coast of Jamaica, while a rain band was hitting the northeast coast of the Dominican Republic. The center of the storm is predicted to move north between Haiti and Cuba.
TRMM shows line of Midwest storms that caused tornadoes in Illinois and Wisconsin November 22
The Tropical Rainfall Measuring Mission (TRMM) acquired rain rate data for the strong line of thunderstorms that passed through the upper Midwest of the United States on November 22nd. The storms caused tornadoes that were sighted in Illinois and Wisconsin. The tornado may have overturned a school bus near Caledonia, Illinois; six children were taken to the hospital. Observers took pictures and video of the tornado on the ground near Rock Cut State Park outside of Rockford, Illinois. In Wisconsin, heavy damage near Union Grove (west of Racine, near the source of the Des Plaines River) was attributed to a possible tornado.
The TRMM image shows the line of thunderstorms about an hour after the tornadoes reported in Wisconsin and Illinois; the line of storms was in central Illinois extending northeast into Michigan. Rockford and Union Grove are near the border of Illinois and Wisconsin.
Typhoon Yasi nearing Australia
Using the TRMM near-real-time Giovanni site (http://disc2.nascom.nasa.gov/Giovanni/tovas/realtime.3B42RT.shtml), which uses the older Giovanni interface format, the ominous shape of Typhoon Yasi's precipitation swirl can be seen bearing down on the hard-hit coast of Queensland, Australia. Yasi is expected to make landfall on Thursday, February 3.
Typhoon Yasi approaches the coast
Utilizing the same Giovanni site as for the above image, this accumulated rainfall image for 00Z-03Z on February 2, 2011 (7:00-10:00 PM U.S. Eastern Standard Time) shows the rainfall track of Yasi as it moved toward the coast of Australia, with an anticipated landfall near Cairns. The higher accumulations on the northeastern side of the rainfall pattern (near New Guinea) indicate that Yasi sped up as it approached the coast, so that less rainfall accumulated. This could be potentially good news for Queensland, already hard-hit by floods, if Yasi does not drop a lot of rain in any one area.
Typhoon Yasi's rainfall over Queensland
24 hours of rain over Queensland from Typhoon Yasi, from 03Z February 2 to 03Z February 3 (03Z converts to 10:00 PM Eastern Standard Time on the previous day). Reports indicate that while devastation was widespread, substantial loss of life was averted by good preparation. However, flooding in subsequent days is still a significant concern. Note that the red color in this image indicates accumulated rainfall in excess of 180 mm (more than 7 inches).
Three different views of rains from Tropical Cyclone Carlos
"Surprise" Tropical Cyclone Carlos dumped record rains on the northwest coast of Australia and the city of Darwin over the past week. At the time that this note is being written, Carlos is still located on the northwest coast of Australia, near Onslow and Exmouth. It is expected to move out to sea and will no longer be a hazard to the Australian citizens.
NASA's Earth Observatory created an image of the rain accumulation from Carlos, and featured it in their Natural Hazards section.
We decided to use three different color palettes with the near-real-time TRMM Multi-Satellite Precipitation Analysis (TMPA-RT) data in Giovanni to look at the same event. These images show how the use of different colors can provide different perceptions of a single geophysical event. The first palette is the "Blue-Red" palette, the second is the "Grayscale" palette, and the third is the "Haze" palette. Note that the color scale is in units of millimeters/hour, and not total accumulation, which is reported to be in excess of 600 mm in some parts of northwest Australia. Carlos is a slow-moving storm, and that has allowed it to generate record rainfall totals.
MODIS Terra and Aqua Aerosol Optical Depth images of Iraq dust storm, March 2011
The Earth Observatory frequently provides users with inspiration for the use of Giovanni, and an early spring dust storm in Iraq in the first days of March 2011 was one of those events. The Image of the Day article entitled "Dust Travels from Iraq to Iran" showed true color images of the dust storm on March 3rd and March 4th. To look at this event, aerosol optical depth (AOD) images for the period March 2-5 were generated, to provide more data in the image than would be seen in a single day.
The results are interesting. North of the large and dark Mileh Tharthar wetland, the storm is clearly seen in the true color images on March 3. But the MODIS AOD images do not show significantly elevated AOD in that location. Instead, higher AOD values are seen in southeastern Iraq. (Mileh Tharthar is the northern of the two large central lakes in Iraq that can be seen in the Giovanni images.)
As these are images averaging all the data for this region over March 3-5, it is likely that when the storm was near ground level and the dust was thick on March 3, it was interpreted as land. The dust likely mixed higher into the atmosphere on subsequent days as it was transported to the southeast, resulting in the elevated AOD values seen in eastern and southeastern Iraq, southern Iran, and over the Persian Gulf.
MODIS-Terra Aerosol Optical Depth, March 3-5, 2011
MODIS-Aqua Aerosol Optical Depth, March 3-5, 2011
Massive dust storms affect Kuwait and Saudi Arabia
Several recent large dust storms have impacted the Arabian region, particularly the oil-rich country of Kuwait. These storms have been so fierce that airports have been closed and oil exports have been curtailed.
This report describes the most recent storms and their economic impact: Dust storm halts Kuwait oil exports
NASA' s Earth Observatory has true-color Moderate Resolution Imaging Spectroradiometer (MODIS) images of dust storms that occurred on March 26-27 and April 13; the April 13 storm is the one described in the linked article.
Arabian Sand Storm (March 26-27)
Dust storm in the Middle East (April 13, 2011)
The standard MODIS aerosol optical depth (AOD) data product does not return data over brightly-reflective desert regions, as can be seen in the images immediately above. However, the MODIS "Deep Blue" aerosol data product has an algorithm that works over the optically bright desert regions. Using the Deep Blue aerosol data product, a colleague at the GES DISC who has friends in the region observed the AOD signature of the late March dust storm. The image was annotated using Microsoft Powerpoint.
Videos of the event (such as this one) show daytime transformed to nighttime as the thick cloud of dust descended over the countryside.
TRMM precipitation maps for April 2011 show heavy rain pattern in central United States
Catastrophic killer tornadoes and record-breaking floods dominated the weather news in the last days of April and the beginning of May 2011 in the United States. Using the experimental Tropical Rainfall Measuring Mission (TRMM) Multi-Satellite Precipitation Analysis data product, TMPA-RT, precipitation maps for the month of April and the first and second halves of the month were created. These maps show how much the rainfall intensified in the latter part of April, a period that included the tornado outbreaks in Mississippi and Alabama, and which contributed to the rampaging Ohio and Mississippi River flood waters in the first days of May.
TMPA-RT precipitation map for the month of April 2011 over the United States.
TMPA-RT precipitation map for April 1-15 over the United States.
TMPA-RT precipitation map for April 15-30 over the United States. Note that the color palette scale is different than for the image above; the highest levels of precipitation designated by red and magenta in the April 15-30 image indicate approximately twice the rainfall accumulation as the same colors indicate in the April 1-15 image.
Mid-Atlantic rainfall, May 16-20, 2011
A persistent, slow-moving low pressure system brought a lot of rain to the Mid-Atlantic region (relatively speaking, compared to the Midwest's rain and flood disaster) in mid-May 2011. The Potomac River was also in flood stage on May 19 and 20, with flooding on the upper tidal Potomac River, and the Georgetown flood walls were raised. (Earlier in the year when rains caused the Potomac to flood, the walls weren't raised, causing damage to some riverside buildings and restaurants).
The first TRMM accumulated rainfall map shows that most of the rain fell over West Virginia and Virginia. Several storm bands moving west-northwest dropped a lot of rain on central Virginia. There was so much rain in central Virginia that it looks like most of the state of Maryland didn't get any!
TRMM 3B42RT accumulated rainfall map, May 16-20, 2011, over the Mid-Atlantic region
Because here Greenbelt (where Goddard Space Flight Center is located) and central Maryland there was definitely some rain, Giovanni was used to zoom in on the Chesapeake Bay region. It still looks like there wasn't much rainfall in the upper Chesapeake Bay region around Baltimore and Havre de Grace. (Baltimore is located at approximately 39.3 degrees N, 76.6 degrees W. The reason for this appearance is the higher precipitation values at the edges of the image. Giovanni dynamically adjusts the color palette to cover the full range of data values.
TRMM 3B42RT accumulated rainfall map, Chesapeake Bay region, May 16-20, 2011
A deeper zoom shows that there was some rain during this period, but the area between Washington D.C. (the oblong shape in the lower left corner) and Baltimore still received a surprisingly small amount of rain during this week-long weather event. Well, now you can see from this TRMM data presentation what meteorologists mean when they say "scattered showers and thunderstorms across the region for the next few days".
TRMM 3B42RT accumulated rainfall map, upper Chesapeake Bay region, May 16-20, 2011
CALIPSO Vertical Feature Mask shows aerosols and clouds for intense dust and pollution event in Hong Kong
On March 22, 2010, a dust storm that had originated in the Gobi Desert and north-central China swept through Hong Kong and out to sea, causing widespread air pollution and haze in the city of Hong Kong, the island of Taiwan, and parts of Japan. A Giovanni user who works in Hong Kong said that this episode is one of two episodes under study, and "it is the worst episode recorded in Hong Kong so far". The Vertical Feature Mask visualization using CALIPSO lidar data was used to show the vertical distribution of dust aerosols in the atmosphere for this event. Using the latitude/longitude scale under the image, which represents a vertical "slice" of the atmosphere along the CALIPSO ground track, the location of Hong Kong can be found at 22.3° latitude, 114 longitude. Fortuitously, CALIPSO went directly over Hong Kong on this date and time. The yellow color of features identified as aerosols is mixed with the blue color of features identified as clouds.
News reports and images show the it was very cloudy and hazy in Hong Kong on March 22:
The picture of pollution (Wall Street Journal article)
Hazy Hong Kong skyline on March 22, 2010 (image)
The MODIS image below the Vertical Feature Mask image, acquired from the NASA Earth Observatory, shows the dust storm two days earlier, over central China south of Beijing.
Vertical Feature Mask plot for 22 March 2010, showing dust in Hong Kong and central China (generated by Giovanni 3 using data from CloudSat). Click on the image to see it larger.
MODIS-Terra image of central China dust storm, March 20, 2010, from the NASA Earth Observatory.
Record spring 2011 precipitation in the United States
A Wunderblog post by Dr. Jeff Masters on June 14, 2011 described the National Oceanic and Atmospheric Administration's (NOAA) report that the meteorological spring of 2011 was the wettest on record for the continental United States. (Meteorological spring is the months of March, April, and May, while astronomical spring is the period between the spring equinox and the summer solstice.) The NOAA report gave the statewide rankings in terms of how much precipitation each state received, but did not provide actual numbers. Using the Tropical Rainfall Measuring Mission 3B42RT Near-Real-Time monitoring product, an estimate of the actual amount of precipitation can be made using data acquired by satellite-borne instrumentation:
Using the color palette above, a rough calculation shows that for the highest values shown (dark orange), the precipitation amounted to over a "yard" of rain, about 38 inches (or in metric terms, just under a meter). In either English or metric units, this volume of rain contributed to the floods in the Ohio and Mississippi River watersheds. What is also noteworthy in this image is the sharp boundary between heavy precipitation and virtually no precipitation in the central plains states south through Texas. Obviously, some of this rain was delivered by powerful thunderstorms that spawned tragically destructive tornadoes in several states in the South and Midwest.
Rainfall from Tropical Storm Arlene heavy in Mexico, light in Texas
The first named storm of the Atlantic hurricane season, Tropical Storm Arlene, made landfall on the eastern coast of Mexico, south of Tampico near Cabo Rojo. Mexican authorities warned of the possibility of floods and landslides caused by heavy rains from Arlene. Further north, officials in Texas hoped that the edges and remnants of Arlene could bring rain to the drought-stricken southern parts of the state. As of July 1, only a light amount of rain from Arlene had fallen in far southern Texas, as the storm rained out over the mountains of Mexico.
The first image shows the rainfall from Arlene for the period 00Z June 28-21Z June 30. Times expressed with "Z" are Universal Time (UT). Eastern Daylight Time is -4 UT, so this period is from 8 PM June 27 to 5 PM June 30 EDT.
The outer edges of Arlene provided a small amount of rain to far southern Texas during this time period. Note that the color palette scale is much less for this image than the image above.
NO2 in New Mexico, June 27-29, 2011
New Mexico could have used the rain from Tropical Storm Arlene to help quench fires burning in that state and across the border in Arizona. The fierce Las Conchas fire threatened the town and national laboratory in Los Alamos, while smoke from Arizona's immense Wallow Fire and the Donaldson Fire in central New Mexico also created nitrogen dioxide (NO2 ) detectable by the Ozone Measuring Instrument (OMI). Nitrogen dioxide pollution is converted by sunlight to nitrogen oxide (NO), and NO + NO2 concentrations are expressed commonly as NOx . NOx is converted by sunlight into low-level ozone (O3), forming haze and also causing respiratory irritation. Emissions from coal-burning power plants located in northwest New Mexico are also visible in this image, which was labeled in MS Powerpoint.
Rain track of tropical storm and hurricane Irene, August 20-23, 2011
A Giovanni user image shows the rain track from tropical storm and now-hurricane Irene over the past three days, August 20-23, 2011. Despite damaging winds, Puerto Rico did not receive a large amount of precipitation from Irene. The Virgin Islands, however, where transportation tycoon Richard Branson's island mansion was destroyed by a lightning-sparked fire, did receive a considerable amount of rain from Irene.
Two images of hurricane Irene's accumulated rainfall
Following the passage of Hurricane Irene over the weekend, the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis - Real Time product (TMPA-RT) was used to view the full accumulated rainfall track of hurricane Irene. The track shows Irene from its tropical storm origins to its destructive and dangerous path up the East Coast of the United States. To help with the color scale, 100 millimeters is about 4 inches.
Just for fun, we put an open pitcher of water on the back deck of our house in Elkridge, Maryland to see how much rainfall we received. We measured the accumulation at about 5.25 inches (133 millimeters). The image below shows the TMPA-RT data product for the states of Maryland and Delaware, and parts of North Carolina, Virginia, West Virginia, Pennsylvania, New Jersey, and New York. The location of Elkridge, Maryland (just south of Baltimore) marked. The color scale indicates that the Elkridge region received between 120-140 millimeters of rain – right in the correct range for the amateur measurement we made. To "correlate" this measurement, the official reported accumulated rainfall from Irene at Baltimore Washington International Thurgood Marshall Airport was 4.69 inches (119 millimeters). So give-or-take a few millimeters, the TMPA-RT product appears a pretty accurate estimate of Irene's rainfall in Maryland.
Time-series of SeaWiFS aerosol optical thickness south of Iceland, 1997-2002
A just-published study of dust events originating from Iceland indicated that the island is a major source of dust for the North Atlantic. This dust export can provide iron to augment phytoplankton growth. The source of the dust is the glacial outwash plains from the many ice fields of Iceland. According to the paper, retreat of the glaciers would be expected to lead to an increase of dust emissions.
The dust was monitored by a station on the island of Heimaey, just south of the main island of Iceland (and also the site of the famous Eldfell eruption in 1973; see the U.S. Geological Survey PDF document "Man Against Volcano"). The paper noted that the dust exports were greatest in spring and early summer. The paper includes a Moderate Resolution Imaging Spectroradiometer (MODIS) image of dust plumes from southern Iceland, observed on October 5, 2004.
Data products from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) include atmospheric aerosol data that were generated as part of the atmospheric correction process for the ocean radiance data that was acquired and processed by this mission. Utilizing Giovanni, these data allow a remote-sensing look at the time period and region discussed in the paper. The data product used was the aerosol optical thickness at 865 nm (AOT 865), from the Ocean Color Radiometry 8-day Data Product Visualization portal.
Screen capture of the region selected to generate the time series:
The time series shows peaks in the values of AOT 865 occurring in the spring, as discussed in the paper. The gaps in the time series are due to the fact that data was not collected during the winter when low solar zenith angles prevented the acquisition of accurate ocean radiance data. Thus, some of the highest values are observed just when data collection commenced in the spring at this latitude.
New aerosol data products based on a reanalysis of SeaWiFS data using advanced algorithms will soon be available in Giovanni.
Reference: Joseph M. Prospero, Joanna E. Bullard, and Richard Hodgkins: High-latitude Dust Over the North Atlantic: Inputs from Icelandic Proglacial Dust Storms. Science, Volume 335, 2 March 2012, 1078-1082. [Abstract - links to full paper, which may require personal or institutional subscription to view]
Article (with video interview) from PhysOrg: New study links dust to increased glacier melting, ocean productivity
MODIS-Terra spots a healthy phytoplankton bloom off Antarctica
A recent news article in the scientific press described a large phytoplankton bloom off the coast of Antarctica. This late-season bloom was located off of Cape Darnley, near the Amery Ice Shelf.
The ocean color radiometry 8-day data portal was used to examine the bloom. The most recently available 8-day data period is February 18-25; the next 8-day, February 26-March 4, should be available very soon. The MODIS-Terra true color image provided by the Australian Antarctic Division was acquired on March 4.
Click on the images below to see them full size.
MODIS-Terra image of phytoplankton bloom off of Cape Darnley, Antarctica, March 4, 2012. The inset image shows the location of the image on the coast of Antarctica.
Giovanni chlorophyll a concentration image for February 18-25, 2012, of the circumpolar Southern Ocean. The phytoplankton bloom was near the Amery Ice Shelf, the large "cut" on the right side of the Antarctic coast in this image.
Giovanni chlorophyll a concentration (chl a) image for February 18-25, 2012, of the Antarctic coast. The island of Kerguelen is at center left. Increased chl a concentrations can be see off the coast.
Giovanni chlorophyll a concentration (chl a) image for February 18-25, 2012, showing Cape Darnley and the Amery Ice Shelf. Elevated chl a concentrations off the edge of the ice shelf can be seen here. The white area just off of Cape Darnley could be the phytoplankton bloom seen in the March 4 MODIS-Terra image, and interpreted as cloud due to its high reflectivity.
Giovanni euphotic depth image for February 18-25, 2012, for the Cape Darnley - Amery Ice Shelf region. Lower values of euphotic depth indicate increased light absorption and scattering by phytoplankton.
Giovanni absorption coefficient for phytoplankton (aph) image for February 18-25, 2012, for the Cape Darnley - Amery Ice Shelf region. Higher values of aph indicate light absorption by phytoplankton.
Giovanni normalized fluorescence line height (nFLH) image for February 18-25, 2012, for the Cape Darnley - Amery Ice Shelf region. The very high values of nFLH seen adjacent to the ice shelf edge indicate a healthy, growing phytoplankton population.
Giovanni particulate organic carbon (POC) image for February 18-25, 2012, for the Cape Darnley - Amery Ice Shelf region. Increased values of POC indicate higher populations of phytoplankton, consistent with the observation of the phytoplankton bloom.
Cape Darnley - Amery Ice Shelf bloom update
The phytoplankton activity off of Cape Darnley and the Amery Ice Shelf appears to have waned during the February 26-March 4 period, with some heightened activity located nearby around Drygalski Island. The area where the bloom was observed is still white (see above), potentially due to the reflectivity of the bloom or sea ice. New observations of a similar feature occurring off the Princess Astrid coast (see posting below) indicate that both this feature and that near the Princess Astrid Coast could be due to phytoplankton attached to floating sea ice.
Click on any image to see it full-size.
MODIS-Aqua chlorophyll a image of the Cape Darnley - Amery Ice Shelf region for the 8-day period February 26 - March 4, 2012. The highest concentrations of chl a are seen around Drygalski Island, at approximately 65 degrees South, 93 degrees East.
MODIS-Aqua absorption coefficient for phytoplankton, February 26-March 4, 2012.
MODIS-Aqua normalized fluorescence line height (nFLH), February 26-March 4, 2012. Heightened nFLH is clearly visible near Drygalski Island.
MODIS-Aqua particulate organic carbon, February 26 - March 4, 2012.
MODIS-Aqua euphotic depth, February 26-March 4, 2012.
More phytoplankton and green ice off the Princess Astrid coast
NASA Earth Observatory described a MODIS image depicting another area of green ice and water observed off the Princess Astrid coast of Antarctica:
Greening the Princess Astrid Coast
Using the same data products as shown above, it is clear that there is a lot of growing phytoplankton in this area. As is noted in the discussion, this is a time when sea ice should be forming, not breaking up and overturning, and it's very late in the growing season (the length of daylight and the sun angle are both decreasing rapidly), so this high level of observed phytoplankton activity seems unusual. But scientists enjoy figuring out the unusual, so these observations appear to be quite intriguing to the oceanographic community.
MODIS-Aqua chlorophyll a image of the Princess Astrid coast region of the Antarctic coast, February 26-March 4, 2012. The white area between the coastline and the open ocean water (where chl a concentrations are shown) is sea ice.
MODIS-Aqua phytoplankton absorption coefficient (aph) image of the Princess Astrid coast of Antarctica, February 26 - March 4, 2012.
MODIS-Aqua normalized fluorescence line height (nFLH) image of the Princess Astrid coast of Antarctica, February 26 - March 4, 2012. The large areas of red indicate active phytoplankton along the sea ice edge, some of which may be attached to the sea ice.
MODIS-Aqua particulate organic carbon (POC) image of the Princess Astrid coast of Antarctica, February 26 - March 4, 2012. Sea ice phytoplankton communities are among the most productive in the entire world ocean.
MODIS-Aqua euphotic depth image of the Princess Astrid coast of Antarctica, February 26-March 4, 2012. Absorption of light by phytoplankton reduces the depth to which light penetrates in ocean waters.
MODIS-Terra Aerosol Optical Depth and Mass Concentration show drift of smoke from New Mexico fires
The Whitewater-Baldy fire in New Mexico's Gila National Forest has set a record of dubious distinction, becoming the largest forest fire in the state's history. The Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Terra satellite captured a remarkable picture of the thick smoke from the fires on May 23, 2012, as described by NASA's Earth Observatory:
Fire Rages in Gila National Forest
This full-scale image from MODIS shows where the smoke was drifting over New Mexico on May 23.
MODIS does not just take pictures; it also collects data in 36 different wavelengths, and generates numerous data products. Shown below are two MODIS data products, aerosol optical depth and mass concentration, averaged over the period May 22-24, 2012, over New Mexico. Because MODIS is better at detecting aerosols from smoke higher in the atmosphere, the highest concentrations due to the smoke from the fires are not where the fires are burning, but where the smoke is drifting eastward and higher in the atmosphere.
The MODIS-Terra AOD image shows high aerosol concentrations over southeastern New Mexico. The Gila National Forest, where the fires were burning, is in southwestern New Mexico at approximately 33.5 N latitude, 108.5 W longitude.
The MODIS-Terra mass concentration data product provides an estimate of the mass of aerosol above a given area of land in units of micrograms per square centimeter. This expression of the amount of aerosol in the atmosphere is termed the columnar mass concentration.
NO2 from Colorado wildfires in the Rocky Mountains
During June 2012, almost exactly a year since large wildfires occurred in New Mexico (see images above), massive wildfires broke out along the Front Range of the Rocky Mountains in Colorado. On the day these images are being added to the page, the Waldo Canyon fire has raged down the mountainside in Colorado Springs, burning numerous homes, and a new fire has broken out near Boulder, potentially endangering the NOAA National Center for Atmospheric Research (NCAR).
Nitrogen dioxide (NO2) occurs in conjunction with fires, produced by oxidation of atmospheric nitrogen during combustion. The 10-day averages of the Ozone Measuring Instrument (OMI) NO2 data products for the period June 15-24 were created using the Giovanni OMI L2G (Level 2 Gridded) data portal. The images show elevated NO2 concentrations from two major fires on the Front Range, the High Park fire to the north and the Waldo Canyon fire in central Colorado. To the southwest, higher NO2 concentrations are seen from the Weber and Little Sand fires near Durango. South of the border in New Mexico, elevated NO2 is likely from the coal-fired Four Corners electricity generating station.
The Earth Observatory Image of the Day for June 26, "Wildfires Across Colorado", shows smoke plumes from the fires observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite.
10-day average, June 15-24, 2012, of NO2 column amount data over Colorado, showing elevated NO2 concentrations associated with wildfires in the Rocky Mountains. (Click on the image to see it full-size.)
10-day average, June 15-24, 2012, of tropospheric NO2 column amount data over Colorado, showing elevated tropospheric NO2 concentrations associated with wildfires in the Rocky Mountains. (Click the image to see it full-size).
Snapshots of the derecho from Giovanni North American Land Data Assimilation System (NLDAS) Hourly Data Portal
The Giovanni North American Land Data Assimilation System (NLDAS) Hourly Data Portal provides output from hydrological models that are used to examine the hydrological effects of weather and climate. The input to the models consists of "gauge-based observed precipitation data (temporally disaggregated using Stage II radar data), bias-correcting shortwave radiation, and surface meteorology reanalyses" (from the NLDAS Concept/Goals page).
During the afternoon and evening of June 29, 2012, a powerful thunderstorm event called a "derecho" traveled across several states in the Midwest and Mid-Atlantic, creating a path of destruction almost 600 miles long and 100 miles wide. Hundreds of thousands of people lost electrical power due to downed trees and downed power lines, and there were several tragic fatalities. The main cause of damage and destruction was the 80-100 mile per hour wind gusts accompanying the storms. The storms also produced heavy rain described as "blinding", although due to their rapid rate of movement (nearly 60 miles per hour), the rainfall did not cause appreciable flooding.
Using the NLDAS "Precipitation hourly total" data parameter, which has units of kg per square meter (kg /m^2), the hourly progress of the storms can be observed. In the set of hourly images below, the color palette used a maximum value of 15 kg/m^2, to show where the storms were most intense. Two images are shown below the set, which were plotted with the dynamic color palette. These image show the maximum values of hourly total precipitation produced by the storms, and indicate that the storms dramatically intensified for a brief period as they crossed the Ohio/West Virginia border. The final image shows the path of the derecho in the hourly precipitation data, which can be compared to the radar track of the event produced by the National Weather Service. Click on any image to view it full size.
Links to two animations of the hourly precipitation data are provided below, in mp4 and WMV format.
Video animation of NLDAS total hourly precipitation data for the June 29, 2012 derecho event (mp4)
Video animation of NLDAS total hourly precipitation data for the June 29, 2012 derecho event (WMV)
06/29/2012, 14 Z (10:00 AM EDT)
06/29/2012, 15 Z (11:00 AM EDT)
06/29/2012, 16 Z (12:00 PM EDT)
06/29/2012, 17 Z (1:00 PM EDT)
06/29/2012, 18 Z (2:00 PM EDT)
06/29/2012, 19 Z (3:00 PM EDT)
06/29/2012, 20 Z (4:00 PM EDT)
06/29/2012, 21 Z (5:00 PM EDT)
06/29/2012, 22 Z (6:00 PM EDT)
06/29/2012, 23 Z (7:00 PM EDT)
06/30/2012, 00 Z (8:00 PM EDT)
06/30/2012, 01 Z (9:00 PM EDT)
06/30/2012, 02 Z (10:00 PM EDT)
06/30/2012, 03 Z (11:00 PM EDT)
06/30/2012, 04 Z (12:00 AM EDT)
06/30/2012, 05 Z (1:00 AM EDT)
Derecho intensification over central Indiana - total hourly precipitation above 22.5 kg/m2.
Derecho intensification near Ohio/West Virginia border - total hourly precipitation above 39.0 kg/m2.
Path of the Derecho
Composite radar image of the derecho, from the National Weather Service. (Image shown full-size).
Dust from the Sahara crosses the Atlantic Ocean in July 2012
In mid-July 2012, meteorologists noted a large area of dust from the Sahara Desert had crossed the Atlantic Ocean and was heading toward Florida. Webcam images posted to the Accuweather.com news showed the effects of the dust on the Virgin Islands on July 17.
The Moderate Resolution Imaging Spectro-radiometer (MODIS) aerosol optical depth (AOD) data product is very effective at detecting dust aerosols in the atmosphere. Using this daily data product in the Giovanni MODIS Daily data portal, a plot of AOD was created for July 17. Red, orange, and yellow colors indicate higher values of AOD, indicating the presence of dust in the atmosphere. An arrow showing the location of the Virgin Islands was added with Powerpoint. (Click on the image to view it larger.) The white areas over the ocean are gaps between the data-collecting swaths of the MODIS instrument on each of the orbits of the Terra satellite, which carries MODIS, around the Earth.
Giovanni was then used to create plots of AOD for overlapping two-day intervals from July 12 to July 17 to show the movement of the dust across the Atlantic. Two day plots largely remove the gaps between the scanning swaths of the MODIS instrument which are seen in a single daily image, and thus show the position of the dust on each of the two days of the period. (Click on any of these images to see it full-size.) The white area below the dust region is likely persistent clouds in the Intertropical Convergence Zone (ITCZ).
Below the individual images is an animated GIF allowing the movement of the dust to be discerned. At the end of the data period, another large area of dust is seen streaming off the African coast. (The animated GIF is shown full-size.)
Animated GIF image:
Iron fertilization bloom in the north Pacific Ocean, July-August 2012
Reports of a large-scale ocean iron fertilization project in the northern Pacific Ocean off the coast of British Columbia were published in the media in October 2012, such as this article in the UK Guardian. There are clearly significant geopolitical and geophysical issues with regard to this project and its ramifications for the world's climate and environment. Satellite remote sensing provides the capability to observe the progress of this project and its effects on the surface waters of the Pacific Ocean. 'Larger' issues related to this project will likely be subjects for both scientific and political discourse in the future.
Giovanni now has several data products at 8-day temporal resolution that allow greater insight into the dynamics of an artificially-stimulated bloom than has been possible previously. The images shown below show the temporal evolution of this iron-induced phytoplankton bloom.
Each image below can be clicked to provide a full-size version.
The 8-day images for the period July 19-26, 2012, do not show any particular features. The area to watch is approximately 52.5 N, 139 W. Shown below are chlorophyll a concentration (left), absorption coefficient for phytoplankton, aph (center), and normalized fluorescence line height, nFLH (right). Reports in the media indicate that the release of a substance containing trace amounts of soluble iron to these waters by the project commenced in July 2012.
The next period during which some ocean color data were retrieved for this area was August 4-11. Despite the heavy cloud cover, pixels displaying elevated chl a and elevated aph were observed. The images shown below are chl a (left) and aph (right).
The next period provided no useful data. However, the clouds began to clear during the August 20-27 period. (The 8-day images will display data from any valid pixels during the period; the data are averaged if more than one observation is acquired during the period. Thus, cloud cover effects may be reduced in 8-day images as more ocean surface is observed through breaks in the cloud cover). Intriguingly, the main break in the cloud cover offshore occurred directly over the bloom! Shown below are chl a (top row left), aph (top row center), nFLH (top row right), and total absorption, A (bottom row left). The highest values in the nFLH image show where the phytoplankton were most actively growing.
The clouds dissipated over this region of the north Pacific Ocean for the next 8-day period, August 28-September 4, 2012. This low-cloud condition allowed acquisition of a pseudo-true color image from MODIS on August 29. The image and labels are provided by Robert Simmon, NASA Earth Observatory. Looking closely at this image, areas where the water surface appears nearly black occur above and below the lighter-colored bluish-green feature labeled "iron fertilization bloom?". These dark areas are where light absorption by photosynthetic organisms (phytoplankton) is occurring, thus there are lower light values for the MODIS band that is used to create the image, making the water surface appear very dark.
Looking at the Giovanni-generated images for this period indicates some interesting ocean biology took place at this time. Shown below are chl a (top row left), aph (top row center), nFLH (top row right), and A (bottom row left). Note the patchiness of the aph and the overall reduction in A compared to the images from the previous period. This likely indicates decline in the growth of the phytoplankton as the nutrients in the water column were consumed. Unfortunately, data filtering for the nFLH algorithm blocked an interesting area of the bloom.
Two additional data products illustrate some of the interesting features of this period. One data product is remote sensing reflectance at 443 nm, Rrs(443). 443 nanometers is the visible spectral region where absorption by chlorophyll in phytoplankton is greatest, and the values of Rrs(443) are very low in the bloom region. This demonstrates the cause of the 'dark water' observed in the MODIS pseudo-true color image.
The other aspect of interest is the identity of the lighter colored feature in the August 29 MODIS image. Such lighter colors in ocean waters are usually due to blooms of coccolithophores, phytoplankton that create spheres made of calcium carbonate (CaCO3) discs called coccoliths. Coccolithophore blooms reflect light very well, which causes their characteristic appearance. The data product Particulate Inorganic Carbon (PIC) was primarily created to provide data on the occurrence of coccolithophore blooms. The PIC image shows quite well that this feature was likely a coccolithophore bloom. Compare the PIC image to the total absorption image above, where there are only slightly elevated values of A in the area of the likely coccolithophore bloom. An interesting question is whether the reduced nutrient concentrations and other factors in the ocean waters occurring as the primary bloom declined were conducive to the growth of coccolithophores.
Rrs(443) image (left), PIC image (right).
The next period, September 5-12, 2012, shows that the iron-fertilized bloom had almost completely disappeared. However, a very pretty natural eddy has formed closer to the coast of British Columbia, most clearly seen in the nFLH image.
Chl a (left), aph (center), and nFLH (right).
One question that has been posed several times regarding this event is whether the bloom is clearly unusual at this time and location (in the absence of in situ data showing elevated iron concentrations in seawater correlated with the increased phytoplankton growth). A way to address this is to utilize the anomaly analysis capability that was recently added to Giovanni for MODIS-Aqua data. Using this feature, the chlorophyll a concentration anomaly for August 2012 was generated. This figure shows that in the location of the bloom, the chlorophyll a concentration is at least 2-4 milligrams per cubic meter (mg / m3) higher than the 10-year climatological mean, as indicated by the red-orange-yellow values in the figure. Coastal chlorophyll concentrations were also higher than normal. The image below is shown full-size.
Storms cause intense rainfall and flash flooding in Toronto, July 9, 2013
A line of storms moving over the upper Midwestern states of the United States and southern Ontario exhibited some interesting meteorological behavior on July 9, 2013, to the chagrin of residents of Toronto. According to anecdotal comments about this weather event, two storm systems merged into one directly over the city. This system, fed by humid air flowing from the south, resulted in a powerful downpour for several hours, which induced flash flooding in many parts of the city.
The image below is an animated GIF of the Tropical Rainfall Measuring Mission (TRMM) Multi-Satellite Precipitation Analysis in Real Time (TMPA-RT) data product, shown at 3-hour intervals. The animation shows the storms progressing from the Midwestern states, with strong precipitation over northeast Wisconsin. The three images at 2100Z July 8 ("Z" stands for Greenwich Mean Time, GMT), 00Z July 9, and 03Z July 9 show the rainfall over Toronto, which is located on the northwest coast of Lake Ontario.
A YouTube video of this animation (which can be paused during viewing) is here: TRMM Multi-Satellite Precipitation Analysis movie of rainfall causing flash floods in Toronto
Tom Yulsman of the University of Colorado, who writes the column IMAGEO for Discover magazine, wrote about the storms here: Satellite captures storms breaking like a wave over Toronto