GEWEX Ground-based Measurements: Time Series

Within GEWEX products based on the BSRN archive have been calculated, click on "RFA Data Access" at: http://gewex-rfa.larc.nasa.gov/ and then on the flag "Data Products". While the WRMC contains the original data from all existing BSRN stations in full time resolution, the GEWEX products are averages from 35 BSRN sites covering the time till 2005. The GEWEX product generation follows the ideas described as method 7 in the paper:  “Assessment of BSRN radiation records for the computation of monthly means” (Roesch, 2010, doi:10.5194/amtd-3-4423-2010). Two temporal resolutions are available:

• Monthly mean of diurnal cycle (15 minute resolution, based on UTC)
• Monthly means (based on UTC)

The 15-min averages are first computed from the 1-min data for each month. Computation of a single bin requires at least 20% valid data. Minute values that are outside the limits listed in Table 1 are treated as missing values. For shortwave radiation fluxes, values below 0 Wm⁻² during night (solar zenith angle >93) were set to 0 Wm⁻². The monthly mean is then computed by averaging the 96 bins (96×15 min=24 h) that have been produced for each month. The monthly mean is valid only if all bins contain valid values. Performing the computation of the monthly mean diurnal cycle benefits from the typical diurnal cycle of shortwave fluxes, allowing more accurate estimates for incomplete observations. Parameter          Lower bound             Upper bound Global                     -4 Wm⁻²          1.5 S_o · μ^1.2 +100 Wm⁻² Diffuse                    -4 Wm⁻²        0.95 S_o · μ^1.2 +100 Wm⁻² Direct                      -4 Wm⁻²                    S_o · μ^1.2 Reflex                     -4 Wm⁻²            1.2 S_o · μ^1.2 +50 Wm⁻² Long-wave down       40 Wm⁻²                     700 Wm⁻² Long-wave up           40 Wm⁻²                     900 Wm⁻²  Table 1:  Limits used for deriving the GEWEX radiation products. Values outside the indicated intervals were treated as missing. S_o is the solar constant adjusted for Earth-Sun distance. μ is the cosine of the solar zenith angle. A description of the GEWEX-RFA file formats and naming conventions is available on that same page.