12th International Precipitation Conference (IPC12)

Description:

Precipitation remains one of the most challenging processes to model and predict at the local, regional and global scales with significant implications for our ability to quantify water cycle dynamics, inform decision making, and predict hydro-geomorphic hazards in response to extremes. A key to these efforts is adequate observations across space and time scales to constrain and improve models, inform data assimilation efforts, and detect and attribute changes in large-scale dynamics and regional extremes. This special collection of papers is based on advances presented at the 12th International Precipitation Conference (IPC12) which brought together the international community to integrate research, discuss challenges and opportunities, and craft future directions. Innovative contributions in this special collection include advances on three main themes: (1) estimation of precipitation from multiple sensors; (2) water cycle dynamics and predictive modeling at local to global scales; and (3) hydrologic impacts of precipitation extremes and anticipated change. This collection also includes a meeting summary published in BAMS: 10.1175/BAMS-D-20-0014.1.

The support by NSF (grant EAR-1928724) and NASA (grant 80NSSC19K0726) to organize the 12th International Precipitation Conference (IPC12), Irvine California, June 2019, and produce the IPC12 special collection of papers is gratefully acknowledged.

Collection organizer:
Efi Foufoula-Georgiou, Department of Civil and Environmental Engineering, University of California, Irvine (UCI)

12th International Precipitation Conference (IPC12)

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Veljko Petković
,
Marko Orescanin
,
Pierre Kirstetter
,
Christian Kummerow
, and
Ralph Ferraro

Abstract

A decades-long effort in observing precipitation from space has led to continuous improvements of satellite-derived passive microwave (PMW) large-scale precipitation products. However, due to a limited ability to relate observed radiometric signatures to precipitation type (convective and stratiform) and associated precipitation rate variability, PMW retrievals are prone to large systematic errors at instantaneous scales. The present study explores the use of deep learning approach in extracting the information content from PMW observation vectors to help identify precipitation types. A deep learning neural network model (DNN) is developed to retrieve the convective type in precipitating systems from PMW observations. A 12-month period of Global Precipitation Measurement mission Microwave Imager (GMI) observations is used as a dataset for model development and verification. The proposed DNN model is shown to accurately predict precipitation types for 85% of total precipitation volume. The model reduces precipitation rate bias associated with convective and stratiform precipitation in the GPM operational algorithm by a factor of 2 while preserving the correlation with reference precipitation rates, and is insensitive to surface type variability. Based on comparisons against currently used convective schemes, it is concluded that the neural network approach has the potential to address regime-specific PMW satellite precipitation biases affecting GPM operations.

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Stephen E. Lang
and
Wei-Kuo Tao

Abstract

The Goddard convective–stratiform heating (CSH) algorithm, used to estimate cloud heating in support of the Tropical Rainfall Measuring Mission (TRMM), is upgraded in support of the Global Precipitation Measurement (GPM) mission. The algorithm’s lookup tables (LUTs) are revised using new and additional cloud-resolving model (CRM) simulations from the Goddard Cumulus Ensemble (GCE) model, producing smoother heating patterns that span a wider range of intensities because of the increased sampling and finer GPM product grid. Low-level stratiform cooling rates are reduced in the land LUTs for a given rain intensity because of the rain evaporation correction in the new four-class ice (4ICE) scheme. Additional criteria, namely, echo-top heights and low-level reflectivity gradients, are tested for the selection of heating profiles. Those resulting LUTs show greater and more precise variation in their depth of heating as well as a tendency for stronger cooling and heating rates when low-level dBZ values decrease toward the surface. Comparisons versus TRMM for a 3-month period show much more low-level heating in the GPM retrievals because of increased detection of shallow convection, while upper-level heating patterns remain similar. The use of echo tops and low-level reflectivity gradients greatly reduces midlevel heating from ~2 to 5 km in the mean GPM heating profile, resulting in a more top-heavy profile like TRMM versus a more bottom-heavy profile with much more midlevel heating. Integrated latent heating rates are much better balanced versus surface rainfall for the GPM retrievals using the additional selection criteria with an overall bias of +4.3%.

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