Intermittency in precipitation: duration, frequency, intensity and amounts of precipitation using hourly data.
Intermittency is a core characteristic of precipitation, not well described by data and very poorly modeled. There is a need to properly represent the phenomena and processes responsible for precipitation either explicitly or implicitly (parameterized). Detailed analyses are made of near-global gridded (about 1°) hourly or 3-hourly precipitation rates from two observational datasets (TRMM 3B42v7 3-hourly, and CMORPH (v1.0 CRT) hourly both of which have been revised and bias corrected, and from special runs of the CESM model from January 1998 to December 2013 to obtain hourly values to explore the intermittency of precipitation: the frequency, intensity, duration and amounts, and compare with observed estimates. The latter differ somewhat but both are considerably different from the model, which has too much precipitation overall, and it precipitates far too often at low rates and not enough for intense rates, with the divide about 2 mm/h. A focus is on the duration of events, and a new metric is proposed based upon the ratio of the frequency of precipitation at certain rates (0.1 to 2 mm/h) for hourly vs 3-hourly vs daily amounts. A comparison is made for all products of the conditional probability of precipitation (given previous precipitation) for various thresholds. There is a need to properly represent the phenomena and processes responsible for precipitation either explicitly or implicitly (parameterized).
Date:
22 November 2016, 14:15 (Tuesday, 7th week, Michaelmas 2016)
Venue:
Atmospheric, Oceanic and Planetary Physics, off Parks Road OX1 3PU
Venue Details:
Dobson Lecture Room
Speaker:
Kevin Trenberth (NCAR)
Organising department:
Department of Physics
Organiser:
Andrew Wells (Atmospheric, Oceanic & Planetary Physics, University of Oxford; & Wolfson College)
Part of:
Geophysical & Nonlinear Fluid Dynamics Seminars
Booking required?:
Not required
Audience:
Members of the University only
Editor:
Andrew Wells
