New Climate Data Record available: GIRAFE v1 – first dedicated global precipitation data product by CM SAF

CM SAF releases its first dedicated global precipitation climate data record (CDR), the Global Interpolated RAinFall Estimation version 1 (GIRAFE v1), providing daily accumulated precipitation and respective sampling uncertainty as well as monthly means from 2002 to 2022 at 1.0° spatial resolution.
CM SAF included global precipitation in its portfolio responding to the outcome of a workshop series “on global precipitation monitoring in a joint European effort”, which took place from 2014 to 2017. This extension of CM SAF activities is now coming to fruition with the release of GIRAFE v1. Following the workshop series’ outcome, it is the first precipitation CDR sprung from a European initiative. Major building blocks of GIRAFE include the homogenisation and quality control of all input streams and the provision of a unique daily sampling uncertainty at 1.0° spatial resolution

Left: Global map of GIRAFE v1 daily accumulated precipitation on 2021/07/13. Right: Global map of the related daily GIRAFE v1 sampling uncertainty. Source: CM SAF

The GIRAFE v1 CDR provides precipitation estimates derived from a combination of passive microwave (PMW) observations onboard polar orbiting satellites and infrared (IR) observations onboard geostationary satellites. The methods for merging these two kinds of input data and for deriving the daily sampling uncertainty are adapted from the Tropical Amount of Precipitation with an Estimate of ERrors (TAPEER) algorithm.
The PMW input to GIRAFE v1 is from various microwave imager and sounder instruments. Precipitation rate estimates are retrieved from the observed PMW brightness temperatures by precipitation retrieval algorithms HOAPS, PNPR-CLIM*, and PRPS. The resulting archives of instantaneous precipitation rate estimates are homogenized using quantile mapping. The IR input to GIRAFE comes from the five geostationary positions forming the Geo-Ring, providing observations along all geographical longitudes. The spatially and temporally highly resolved IR input is trained locally in space and time to detect the occurrence of precipitation using the PMW-based instantaneous precipitation rate estimates. Conditional precipitation rates are computed based on PMW observations only. At latitudes higher than 55°N/S where Geo-Ring IR pixels are extremely distorted, GIRAFE v1 relies only on the PMW input. The final GIRAFE result is gridded daily accumulated precipitation computed from the (IR-based) fraction of precipitation and the conditional precipitation rate. Additionally, 1° x 1° monthly mean values of the daily accumulated precipitation are provided. The daily accumulated precipitation features the above-mentioned dedicated, unique sampling uncertainty at the same resolution in space and time, which is based on the analysis of decorrelation scales in space and time in the IR-based precipitation fields.

* The PNPR-CLIM algorithm has been developed by CNR-ISAC in the C3S_312b_Lot1 Copernicus project.

The data record can be ordered via the Web User Interface

More information on the data record is available from the DOI page: https://doi.org/10.5676/EUM_SAF_CM/GIRAFE/V001 .

Documentation:

• Roca, R. et al. Merging the Infrared Fleet and the Microwave Constellation for Tropical Hydrometeorology (TAPEER) and Global Climate Monitoring (GIRAFE) Applications. In: Levizzani, V., Kidd, C., Kirschbaum, D.B., Kummerow, C.D., Nakamura, K., Turk, F.J. (eds) Satellite Precipitation Measurement. Advances in Global Change Research, vol 67. Springer, Cham. https://doi.org/10.1007/978-3-030-24568-9_24
• Konrad, H. et al., GIRAFE v1: a global climate data record for precipitation accompanied by a daily sampling uncertainty. in preparation for ESSD, 2024

GIRAFE v1 - Product User Manual (PUM)
GIRAFE v1 - Validation Report (VAL)
GIRAFE v1 - Algorithm Theoretical Basis Document (ATBD)

HK / April2024