The Impact of Atmospheric Rivers on Soil Moisture in California's Russian River Basin
Abstract
The manner in which a watershed responds to precipitation depends on the amount of water the soil in the watershed can store. The NOAA Hydrometeorological Testbed (HMT) has made continuous soil moisture observations in the Russian River basin of California at Healdsburg, CA since December 2003. Extreme precipitation events in the Russian River basin are associated with the land fall of Atmospheric Rivers (ARs). Unique long-term observations of winds aloft plus vertically integrated water vapor (at Bodega Bay on the coast) are combined to calculate “bulk water vapor transport” with hourly time resolution over nearly 6 years. These data are used to objectively determine the onset time of strong upslope water vapor flux events lasting at least 8 hours, i.e., conditions that are characteristic of landfalling ARs. While previous studies have shown a strong connection between landfalling ARs and heavy rain in the region, and all flood events on the Russian River since 1998 have been associated with landfalling ARs, no studies have yet examined the relationship to soil moisture changes. This is important because dry soil conditions can preclude the generation of extreme runoff even when an AR and associated heavy rains strike the region. To explore this, composite time series (4-days long) are created for upslope water vapor flux, precipitation and soil moisture. The composites are developed using events where the observed bulk upward water vapor flux was ≥ 15 cm m s-1 and the integrated water vapor (IWV) ≥ 2 cm for a time period ≥ 8 hours. The composites are stratified by season for the periods DJF, MAM, JJA, and SON because the soil state in the Russian River basin varies considerably during the year. The maximum soil moisture values in the basin are typically observed during the DJF time period when ARs are also more frequently observed. The compositing methodology and the composites themselves will be described at the conference.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.A53B0206Z
- Keywords:
-
- 1840 HYDROLOGY / Hydrometeorology;
- 1866 HYDROLOGY / Soil moisture;
- 3322 ATMOSPHERIC PROCESSES / Land/atmosphere interactions