Raindrops Are NOT Falling on Our Heads

Project Team: Western U.S. Disasters Team
Team Location: NASA Jet Propulsion Laboratory, Pasadena, California

This image depicts the vapor pressure deficit in the southwest United States for the month of August 2012. Image Credit: Western U.S. Disasters Team.

This image depicts the vapor pressure deficit in the southwest United States for the month of August 2012. Image Credit: Western U.S. Disasters Team.

Authors:
Julie Sanchez
Mark Barker
Rosemarie Wrigley

Mentors/Advisors:
Stephanie Granger (NASA Jet Propulsion Laboratory)
Ali Behrangi (NASA Jet Propulsion Laboratory)

Abstract:
Droughts in California and the Southwest United States have had severe impacts on state economies and water resources. In 2014, the state experienced abnormally dry conditions due to a 2013 drought that persisted throughout the next year. In 2014 alone, California is expected to have lost $2.2 billion and have experienced a net water shortage of 1.6 million acre-feet. Decision-makers in California and the Southwest have expressed increasing concerns with detecting and monitoring drought severity and understanding the conditions that lead to drought.  The objective of this project was to characterize meteorological drought within California and the Southwestern United States using Vapor Pressure Deficit (VPD) calculations as a drought index. VPD has been proven to be a reliable drought indicator for California and Southwest United States because the severity of drought conditions is dependent on the amount of available moisture in the atmosphere (Weiss et al, 2012). The Atmospheric Infrared Sounder (AIRS) retrieves measurements of all the atmospheric variables used in the VPD algorithm. Data records from AIRS were processed twice daily and easily accessible through NASA’s Mirador data search tool. Using the Level 3 data version 6 from AIRS, relative humidity and surface air temperature data were retrieved to calculate Vapor Pressure Deficit anomaly (VPDa) maps using ArcGIS. The data from these Vapor Pressure Deficit maps were then compared with data from the National Oceanic and Atmospheric Administration’s National Climatic Data Center and analyzed for any significant correlations.  The analysis also incorporated case studies such as the 2010 Texas drought, 2012 Great Plains drought, and the current drought in California (2014). Comparing known past droughts with the VPD anomaly maps indicated the usefulness of VPD as a drought index. The creation of accessible VPD maps for the end-users and the general public allowed for a more realistic plan of action for Western states dealing with disastrous climatological conditions.

 

 

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