Surface radiation budget of the SGP ARM Climate Research Facility

Description

Our goal is to develop a climatology of the monthly surface radiation budget at the SGP extended facilities of at least 10 years. A few of the sites we begin with (Pawhuska, El Reno, Plevna, etc.) were selected because of their comparatively homogeneous surface properties based on a 1998 field study (Duchon and Hamm 2006). The surface radiation budget is the sum of a shortwave budget and longwave budget. All upward and downward components of radiation are measured with the SIRS instrument. Surface albedo is computed from the shortwave components. The procedure for obtaining a monthly budget is as follows. A day for accumulating shortwave radiation begins with the first minute an upward or downward component of radiation is greater than zero and ends when the component again becomes negative. There are three components of downward shortwave radiation: global sky, direct solar, and diffuse sky. A second estimate of global sky radiation can be computed from direct solar and diffuse sky. There is one upward component. Each component is summed minute-by-minute throughout the course of a day, yielding a daily sum in units of MJ/m2. Each daily sum is added to produce two monthly sums of global sky radiation. The procedure for obtaining daily and monthly sums of upward and downward longwave radiations parallels that for shortwave, except that each daily sum is derived from 1440 minutes. This investigation should provide insight into regional climate change in terms of the radiation budget on the time scale of a decade. We envision producing for each month at each site a figure of monthly summaries providing the data for climatological analyses. A potential problem in developing a high-quality climatological surface radiation data set is the occurrence of bad or missing data. In either case, a replacement value has to be estimated for each bad or missing datum. We will be using Pawhuska as a testbed and example for this poster.