The effects of sampling frequency on the climate statistics of the European Centre for Medium-Range Weather Forecasts

Journal Article · Sun Dec 20 04:00:00 EST 1992 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/92JD02020· OSTI ID:7026172

Phillips, T J; Gates, W L ^[1]; Arpe, K ^[2]

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1. Lawrence Livermore National Lab., CA (United States)
2. European Centre for Medium-Range Weather Forecasts, Reading (United Kingdom)

The effects of sampling frequency on the first- and second-moment statistics of selected European Centre for Medium-Range Weather Forecasts (ECMWF) model variables are investigated in a simulation of perpetual July' with a diurnal cycle included and with surface and atmospheric fields saved at hourly intervals. The shortest characteristic time scales are those of ground heat fluxes and temperatures, precipitation and runoff, convective processes, cloud properties, and atmospheric vertical motion, while the longest time scales are exhibited by soil temperature and moisture, surface pressure, and atmospheric specific humidity, temperature, and wind. The time scales of surface heat and momentum fluxes and of convective processes are substantially shorter over land than over oceans. An appropriate sampling frequency for each model variable is obtained by comparing the estimates of first- and second-moment statistics determined at intervals ranging from 2 to 24 hours with the best' estimates obtained from hourly sampling. Relatively accurate estimation of first- and second-moment climate statistics can be achieved by sampling a model variable at intervals that usually are longer than the bandwidth of its time series but that often are shorter than its characteristic time scale. The superior estimates of first-moment statistics are accompanied by inferior estimates of the variance of the daily means due to the presence of systematic biases, but these probably can be avoided by defining a different measure of low-frequency variability. Estimates of the intradiurnal variance of accumulated precipitation and surface runoff also are strongly impacted by the length of the storage interval. In light of these results, several alternative strategies for storage of the EMWF model variables are recommended. 20 refs., 9 figs., 1 tab.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 7026172
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 97:D18; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
540210 -- Environment
Terrestrial-- Basic Studies-- (1990-)
540310 -- Environment
Aquatic-- Basic Studies-- (1990-)
ATMOSPHERIC PRECIPITATIONS
ATMOSPHERIC PRESSURE
CLIMATE MODELS
CLOUDS
DAILY VARIATIONS
ENVIRONMENTAL TRANSPORT
FORECASTING
FREQUENCY DEPENDENCE
HEAT FLOW
MASS TRANSFER
MATHEMATICAL MODELS
MATHEMATICS
OCEANIC CIRCULATION
RUNOFF
SOILS
STATISTICS
VARIATIONS
WEATHER
WIND