The Relationship between Drought Severity, Precipitation, and Aerosol in California

The recent severe drought in California was notably destructive due to especially high temperatures and little precipitation. This drought caused calamitous and far reaching effects for the environment, economy and public health. Unlike previous periods of drought, understanding the causes of the most recent drought can now be accomplished through satellite based measurements. Satellites offer global measurements of precipitation, temperature and aerosol; all of which can be used to estimate drought severity and impact. This paper offers a 14-year climatology of precipitation, the Palmer Drought Severity Index (PDSI) and aerosol. The National Center for Disease Control computes the monthly averaged PDSI for the state of California. Using this climatology of drought severity and MODIS Level 3 aerosol optical depth we can evaluate the impact drought intensity has on aerosol loading. Increased aerosol has significant regional impacts including effects that directly impact communities, such as air quality and visibility, as well as impacts on the regional hydrological cycle by impacting cloud microphysical characteristics and precipitation. Precipitation observations from TRMM and GPCP are also analyzed in relation to PDSI. The type of precipitation, its intensity and duration are all important for determining drought severity and are considered here. The findings suggest a strong correlation between drought and aerosol, meaning that periods in severe drought tend to also correspond to high levels of aerosol. We will also demonstrate precipitation and drought trends over the last 14 years.