New study compares precipitation estimation products to observations to better understand precipitation estimates in areas with complex terrain
The Russian River is an important water resource in northern California that typically relies on a few significant precipitation events each year, often associated with atmospheric rivers, to maintain its annual water supply. Because the annual precipitation in the region is so variable, researchers and water managers need accurate precipitation estimates to input to hydrologic models and inform water management decisions. However, the basin’s location and complex terrain make it difficult to get those precipitation estimates – in situ observations are sparse and mountains inhibit remote sensing by ground radars.
In a new study published in the March issue of the Journal of Hydrometeorology, CIRES and NOAA researchers from the ESRL Physical Sciences Laboratory compare storm total precipitation estimates from two Multi-Radar/Multi-Sensor (MRMS) products (Gauge Corrected and Mountain Mapper) to precipitation estimates from a local rain gauge network for storms impacting the Russian River Basin over two rainy seasons. MRMS is a NOAA precipitation system developed at the National Severe Storms Laboratory and run operationally at the National Weather Service. In about half of the cases examined, estimates produced by the MRMS products compared well to rain gauge measurements, but in the other half they did not. By looking at characteristics of the storms producing the precipitation at large, medium, and small spatial scales, the researchers determined that the MRMS products performed better under certain storm conditions, yet failed to correctly represent the storm precipitation in others.
To figure out why the MRMS products performed better under certain storm conditions, the researchers placed the storms with good and poor MRMS performance into two general categories and then examined the differences between the groups of storms. They found that the position of the parent cyclone impacted where the atmospheric river made landfall and also the direction of the wind towards shore and in the basin. This, in turn, resulted in different terrain interactions and different areas of enhanced precipitation in the two categories of storms. The storms that the MRMS represented accurately were typically deeper and able to be captured better by WSR-88D radars in the region, whereas those storms that the MRMS did not capture well appeared to be mostly comprised of shallower precipitation that occurred below the radar beam.
In regions such as the Russian River Basin, where annual rainfall is highly dependent on a few large storms each year, researchers and water managers need accurate estimates of precipitation because water management decisions must account for the possibility of long-term drought or flooding, as well as agricultural and ecological concerns. In an area with complex terrain that is also relatively far from the nearest radar and inadequately gauged, water managers will benefit from a better understanding of how storm characteristics might impact the distribution of rainfall in the basin and the MRMS’s ability to capture it.
Authors of the journal article "A multiscale evaluation of multisensor quantitative precipitation estimates in the Russian River Basin" are: Janice Bytheway, Mimi Hughes, Kelly Mahoney, and Rob Cifelli of the ESRL Physical Sciences Laboratory.
Posted: March 25, 2019
The Russian River is an important water resource in northern California that typically relies on a few significant precipitation events each year, often associated with atmospheric rivers, to maintain its annual water supply. Because the annual precipitation in the region is so variable, researchers and water managers need accurate precipitation estimates to input to hydrologic models and inform water management decisions. However, the basin’s location and complex terrain make it difficult to get those precipitation estimates – in situ observations are sparse and mountains inhibit remote sensing by ground radars.
In a new study published in the March issue of the Journal of Hydrometeorology, CIRES and NOAA researchers from the ESRL Physical Sciences Laboratory compare storm total precipitation estimates from two Multi-Radar/Multi-Sensor (MRMS) products (Gauge Corrected and Mountain Mapper) to precipitation estimates from a local rain gauge network for storms impacting the Russian River Basin over two rainy seasons. MRMS is a NOAA precipitation system developed at the National Severe Storms Laboratory and run operationally at the National Weather Service. In about half of the cases examined, estimates produced by the MRMS products compared well to rain gauge measurements, but in the other half they did not. By looking at characteristics of the storms producing the precipitation at large, medium, and small spatial scales, the researchers determined that the MRMS products performed better under certain storm conditions, yet failed to correctly represent the storm precipitation in others.
To figure out why the MRMS products performed better under certain storm conditions, the researchers placed the storms with good and poor MRMS performance into two general categories and then examined the differences between the groups of storms. They found that the position of the parent cyclone impacted where the atmospheric river made landfall and also the direction of the wind towards shore and in the basin. This, in turn, resulted in different terrain interactions and different areas of enhanced precipitation in the two categories of storms. The storms that the MRMS represented accurately were typically deeper and able to be captured better by WSR-88D radars in the region, whereas those storms that the MRMS did not capture well appeared to be mostly comprised of shallower precipitation that occurred below the radar beam.
In regions such as the Russian River Basin, where annual rainfall is highly dependent on a few large storms each year, researchers and water managers need accurate estimates of precipitation because water management decisions must account for the possibility of long-term drought or flooding, as well as agricultural and ecological concerns. In an area with complex terrain that is also relatively far from the nearest radar and inadequately gauged, water managers will benefit from a better understanding of how storm characteristics might impact the distribution of rainfall in the basin and the MRMS’s ability to capture it.
Authors of the journal article "A multiscale evaluation of multisensor quantitative precipitation estimates in the Russian River Basin" are: Janice Bytheway, Mimi Hughes, Kelly Mahoney, and Rob Cifelli of the ESRL Physical Sciences Laboratory.
Posted: March 25, 2019