A Cold Spring in 2013
Unlike many recent spring seasons in the United States, spring of 2013 was noted for an absence of indications that warmer weather was on the way. Late spring snowfalls made the news in several locations, with spring blizzards in the Midwest in April, and even a late May snowfall in upstate New York. Many other areas experienced cold snaps and late frosts that imperiled blossoms on fruit trees and early plantings in gardens.
The weather data confirmed our own perceptions that this was a cold spring; according to the National Climate Data Center (NCDC) of the National Oceanic and Atmospheric Administration (NOAA), spring 2013 was much colder than normal for the nation as a whole. (See “Additional Information” at the end of this article.) The NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) archives data from the North American Land Data Assimilation System (NLDAS-2), which can also be examined to find out if they confirm our perceptions of a cold spring.
Figure 1a, the anomaly of 2-meter above ground temperature from NLDAS-2 Primary Forcing for March – May 2013, shows that most areas of the United States (the West Coast and New England were exceptions) had temperatures colder than those of the 30-year NLDAS-2 climatology (which will be subsequently referred to as “normal”). The coldest state was North Dakota, with negative anomalies exceeding 14 oF. NLDAS temperature data for each month of the 2013 spring can also be examined for month-to-month variations. These data indicate that most of the eastern United States was colder than normal during March 2013 (Fig. 1b). In April 2013, cold areas covered almost the entire northern tier of the United States, with the biggest anomaly over North Dakota and adjacent states (Fig. 1c). Most areas of the United States had temperatures nearly normal in May 2013 (Fig. 1d), with temperature anomalies within -2 ~ +2 oF and only a very few small areas above +4 oF.
Figure 1. Anomaly of 2-m above ground temperature from monthly NLDAS-2 Primary Forcing for (a) March - May 2013, (b) March 2013, (c) April 2013, and (d) May 2013. The anomalies are relative to the NLDAS-2 30-year (1980 – 2010) climatology. The units of temperature have been converted from Kelvin to Fahrenheit. NLDAS data were acquired from Giovanni and replotted for this figure. (Click on any image to view it full size.)
The area-averaged hourly time series over the entire United States (Fig. 2) clearly shows, in addition to the diurnal cycle (the daily rise and fall of temperature), that the average temperature of the United States was about 2 oF colder than normal in March and April, and about normal in May (only 0.05 oF warmer). Overall, the area-averaged temperature over the entire United States for spring (March – May) 2013 is 1.3 oF colder.
Figure 2: Time series of 2-m above ground temperature from hourly NLDAS-2 Primary Forcing, area-averaged over the continental United States. The green lines are the temperatures of the NLDAS-2 30-year monthly climatology for March, April, and May; and the red lines are NLDAS-2 monthly average temperatures for March, April, and May 2013. The units of temperature have been converted from Kelvin to Fahrenheit. (Click on the image to view it full size.)
However, climate and weather vary from place to place. North Dakota and adjacent states, for example, experienced a very cold spring. Figure 3 shows that the area-averaged temperature over North Dakota was about 8, 13, and 0.9 oF colder than normal in March, April, and May 2013, respectively; and about 7 oF colder than normal for the entire spring of 2013. Figure 3 also indicates that the area-averaged temperature over North Dakota had 18 daily highs in March and 24 daily highs in April that were below their respective normal temperatures.
Figure 3. Time series of 2-m above ground temperature from hourly NLDAS-2 Primary Forcing, area-averaged over North Dakota. The green lines are the temperatures of the NLDAS-2 30-year monthly climatology for March, April, and May; and the red lines are NLDAS-2 monthly average temperatures for March, April, and May 2013. The units of temperature have been converted from Kelvin to Fahrenheit. (Click on the image to view it full size.)
For year-to-year variability in temperature, an intercomparison of average temperature between the springs of 2012 and 2013 over the United States provides a very extreme example. Spring 2013 was much colder than spring 2012 over most states, with temperature differences greater than 14 oF over the northern Midwest states (Fig. 4a). Figure 4b shows that the temperature differences between March 2012 and 2013 were greater than 24 oF in North Dakota, Minnesota, and nearby states.
Figure 4. Difference in NLDAS-2 2-m above ground temperature (a) between spring (March ~ May) 2012 and 2013 and (b) between March 2012 and 2013. The units of temperature have been converted from Kelvin to Fahrenheit. (Click on either image to view it full size.)
Data and Tools
NLDAS-2 Primary Forcing temperature data are spatially interpolated, temporally disaggregated, and vertically adjusted North American Regional Reanalysis (NARR) temperature data. These data tell a story that is consistent with stories published in NOAA Climate Watch. (See “Additional Information” at the end of the article.)
NLDAS is a collaborative project between NASA Goddard Space Flight Center (GSFC), the National Oceanic and Atmospheric Administration (NOAA), Princeton University, and the University of Washington. All NLDAS data sets available from NASA GES DISC can be accessed from the Hydrology Data Holdings Portal, http://disc.sci.gsfc.nasa.gov/hydrology/data-holdings, using direct ftp, Mirador search and download, Simple Subset Wizard, and Giovanni online visualization and analysis.
The temperature anomaly maps shown in Figure 1 were generated from data downloaded from one of the Giovanni portals. Giovanni is a Web-based application developed by the GES DISC that provides a simple and intuitive way to visualize, analyze, and access vast amounts of Earth science remote sensing data without having to download the data. The Giovanni NLDAS Monthly Portal and Giovanni NLDAS Hourly Portal, featuring, respectively, the NLDAS monthly and monthly climatology data sets and hourly data, enable NLDAS climatology and anomaly analysis and facilitate water and energy cycle studies. For example, the NLDAS monthly portal can directly and quickly generate temperature anomaly maps (Figure 5) for studying the cold spring of 2013. The portal also allows the downloading of Giovanni results by clicking on the “Download Data” tab on the Giovanni results page, for further analysis or image regeneration (e.g., Fig. 1).
. Anomaly of 2-m above ground temperature from monthly NLDAS-2 Primary Forcing for (a) March - May 2013, (b) March 2013, (c) April 2013, and (d) May 2013. The anomalies are relative to the NLDAS-2 30-year (1980 – 2010) climatology. The anomaly plots were generated by the Giovanni NLDAS Monthly Portal
and downloaded directly. Anomaly visualizations may benefit from a different color palette, such as shown in Figure 1, compared to Giovanni’s default “Rainbow” palette shown here. (Click on any image to view it full-size.)
Additional information can be found at NOAA ClimateWatch Magazine, which has published a series of stories about the spring 2013 weather.
Questions or comments? Email the NASA GES DISC Help Desk: firstname.lastname@example.org