In California, the seasonal variation of precipitation can be basically described as dry in the summer and wet in the winter (Fig. 1). Droughts can occur when precipitation is persistently below normal, such as in this winter season in California, which has worsened its water resource shortages. The near-real-time daily, 0.25 degree spatial resolution Tropical Rainfall Measuring Mission (TRMM) Multi-Satellite Precipitation Analysis (TMPA) data product, available at the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC), can be used to monitor the current drought situation in the state.
. Precipitation climatology in Northern California, generated from Giovanni TOVAS (TRMM Online Visualization and Analysis System). The climatology is derived from the 50-year monthly land-only precipitation data set developed by Cort Willmott (http://climate.geog.udel.edu/~climate/
). Click the image to view it full-size.
Two accumulated precipitation maps for the period August 1- February 9 were generated for 2012-2013 and 2013-2014, respectively, using the TMPA daily data product (Fig. 2). Much less precipitation has fallen from August 2013 to February 2014, compared to that of the corresponding 2012-2013 period, especially in Northern California.
Figure 2. Accumulated precipitation for California from August 2012- February 2013 (top) and August 2013-February 2014 (bottom). Much less precipitation has been received in Northern California during the 2013-2014 period, compared to that of the same period a year ago. Note: the bright orange and red dots are spurious heavy precipitation estimates over lakes, such as Lake Tahoe and Pyramid Lake in Nevada. This is a known issue of the data product. Click the image to view it full-size.
The situation is not much better in Southern California. Figure 3 shows less precipitation has been received this year, compared with the same period a year ago, particularly in the coastal region. The ongoing precipitation deficit has resulted in record-breaking droughts throughout California – draining reservoirs, increasing water shortages, and exacerbating forest fires, according to news reports.
Figure 3. Accumulated precipitation for Southern California from August 2012- February 2013 (top) and August 2013-February 2014 (bottom). Less precipitation was received in the 2013-2014 period, compared to that of the same period a year earlier, especially along the coast. High precipitation estimates over the Salton Sea (lower right) are spurious features of the data product. Click the image to view it full-size.
In recent days in February, an atmospheric “river,” also known as the Pineapple Express, has developed between the Hawaiian Islands and California, bringing in some much-needed precipitation. Figure 4 is an animation showing the evolution of the Pineapple Express, as plumes of moisture moved toward the San Francisco area.
Figure 4. Animation, obtained from the Hurricane Data Analysis Tool (http://disc.gsfc.nasa.gov/HDAT), showing the evolution of the Pineapple Express in February 2014. (Image is shown full-size.)
Figure 5 shows daily accumulated precipitation maps for February 7, 8, and 9, 2014. The narrow precipitation band associated with the Pineapple Express, extending from the vicinity of the Hawaiian Islands all the way to Northern California, is visible in each of the images in Figure 5.
Figure 5. Accumulated daily precipitation maps for February 7, 8, and 9, 2014, showing heavy precipitation regions associated with the Pineapple Express, extending from the vicinity of the Hawaiian Islands to Northern California. Click the image to view it full-size.