Diagnosis of High-Time-Frequency CMIP Output

Tuesday, May 13, 2014 - 07:00
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Three-hourly surface pressure from the Coupled Model Intercomparison Project provides insight into simulation of atmospheric tides, including canceling errors that give the right answer for the wrong reason"" (Covey et al. JAS 68: 495 2011 and JAS in press). The latest database also provides 3-hourly 2D fields of near-surface humidity temperature and wind; soil moisture; total cloudiness; evaporation and precipitation; and surface fluxes of energy. It also provides selected 6-hourly 3D fields. (See categories "3hr 6hrLev" and "6hrPlev" in the list at http://cmip-pcmdi.llnl.gov/cmip5/data_description.html). These fields enable both the study of surface / boundary layer processes relevant to ecosystems and people and the exploration of connections between these processes and upper atmospheric phenomena. Applying to these new fields the same data processing algorithm used in our atmospheric tide studies (op. cit.) gives a new point of view on the diurnal cycle of hydrology. Observations as well as model output are available at high time frequency on the same data distribution system that supports CMIP the Earth System Grid Federation network (github.com/ESGF/esgf.github.io/wiki; Teixeira et al. BAMS in press). For example comparing 3 hourly precipitation anomalies between models and Tropical Rainfall Measuring Mission observations between 50S and 50N latitude reveals similar space-time patterns and magnitudes but the high-resolution TRMM observations generally have a more complex character. Fourier decomposition in space-time dimensions quantifies these differences between models and observations and makes connections with tides and other atmospheric processes. In a broader sense the CMIP output and associated global observations complement local and regional studies of diurnal hydrology that use ARM and other in situ data (e.g. Kooperman et al. GRL 40: 3287 2013; Zhang and Klein JAS 70: 1297 2013). Work performed under auspices of the Office of Science US Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

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