Incoming radiation in complex terrain
Incoming radiation is an important driver of hydrologic processes, particularly in providing energy that melts snow. In many cases we assume such radiation comes in solely from the atmosphere. However, in complex terrain, long-wave radiation may also come from nearby warm parts of the landscape, supplementing the radiation from the atmosphere.
We helped interpret a set of remotely-sensed land-surface temperature images from the EcoSTRESS satellite to assess the importance of such terrain effects in the East River Watershed, the site of Lawrence Berkeley National Lab's Watershed Function Science Focus Area. That work found that this three-dimensional radiation can account for 1/4 of the incoming long-wave radiation in certain parts of the watershed. This energy may have important effects on water and energy flows in mountain watersheds and is important to consider when we quantify their water and energy budgets.
Estimates of downwelling long-wave radiation from models that calculate it based on both land-surface temperature measurements and terrain effects show clear variation from a lower-resolution "flat" estimate.
Papers & presenations
Feldman, D.R., M. Worden, N. Falco, P.J. Dennedy-Frank, J. Chen, B. Dafflon, H. M. Wainwright (2022), Three- dimensional surface downwelling longwave radiation clear-sky effects in the Upper Colorado River Basin. Geophysical Research Letters, 49, e2021GL094605, https://doi.org/10.1029/2021GL094605
Worden, M., D. Feldman, P.J. Dennedy-Frank, N. Falco, B. Dafflon, J. Chen, H.M. Wainwright and A.G. Konings (2020), Exploring Surface Temperature, Evapotranspiration, and Downwelling Longwave Radiation Heterogeneity in High-Altitude Complex Terrain with ECOSTRESS, Abstract H093-03 presented at 2020 Fall Meeting, AGU, 1-17 Dec.
Feldman, D., H.E. Brindley, P.J. Gero, M. Worden, N. Falco, B. Dafflon, P.J. Dennedy-Frank, H.M. Wainwright and T. L'Ecuyer (2020), Modeling and Observation of Processes that Impact the Far-Infrared in Mid-Latitude, High-Altitude Complex Terrain, Abstract A230-0005 presented at 2020 Fall Meeting, AGU, 1-17 Dec.
Rainfall changes in Jordan
Jordan is one of the water-poorest countries in the world, with less than 25,000 gallons (100,000 liters) of water available per person each year, 1/5 the water scarcity threshold of 125,000 gallons. As part of the Jordan Water Project, we helped assess the rainfall changes in Jordan over the 43 years ending in 2013. We used a set of 58 precipitation gauges spread across the western, more-populated part of the country with statistical tests to show that average annual precipitation across the country is decreasing by ~0.4mm/year. Also, the variability of daily rainfall is increasing by 2-3%. We used multiple hypothesis testing to show that these effects are robust and statistically significant despite doing tests on 58 gauges, each of which has a small chance of incorrectly attributing precipitation variability as a trend. Finally, we used a clustering approach to show that the changes in annual rainfall and variability are somewhat separate; the decrease in annual precipitation is strongest in the southern and eastern parts of the country, while the increase in variability is strongest in the northwest portion of the country. This better understanding of precipitation trends in Jordan is important given the country's limited resources, and has been part of water resources planning that the Jordan Water Project is doing to assist Jordanian government ministries in developing a more reliable water supply for a changing climate.
The decrease in annual precipitation is strongest in the southern and eastern parts of Jordan as seen in the decreasing annual rainfall indicated by red dots in these areas. In the northwest of the country the annual precipitation trends are much more mixed but the variability of daily rainfall is increasing most strongly.
Papers
Rahman, K., S.M. Gorelick, P.J. Dennedy-Frank, J. Yoon and B. Rajaratnam (2015), Declining rainfall and regional variability changes in Jordan. Water Resources Research, 51, 3828-3835, doi.org/10.1002/2015WR017153