Disponer de una buena caracterización climática es un aspecto clave para el seguimiento de los efectos del cambio global sobre todo en ambientes de montaña. Sin embargo, los datos climáticos de muchas de las zonas de montaña proceden de fuentes muy heterogéneas y muy dispersas, lo que hace que el acceso y la descarga de esos datos sean tareas que se tornan a menudo arduas y tediosas. En este trabajo presentamos ClimaNevada, una base de datos robusta sobre información climática en Sierra Nevada, que armoniza, documenta e integra datos climáticos procedentes de estaciones meteorológicas y de sensores. Hemos desarrollado una plataforma que aglutina toda la información y permite la descarga de datos de una forma sencilla y siguiendo la filosofía Open Access. Asimismo, presentamos un caso de estudio en el que se generan series de datos homogéneos a partir de ClimaNevada, para la evaluación de tendencias temporales de la precipitación en Sierra Nevada.

Quantitative Precipitation Estimates (QPEs) from the Integrated Multisatellite Retrievals for GPM (IMERG) provide crucial information about the spatio-temporal distribution of precipitation in semiarid regions with complex orography, such as Catalonia (NE Spain). The network of automatic weather stations of the Meteorological Service of Catalonia is used to assess the performance of three IMERG products (Early, Late and Final) at different time scales, ranging from yearly to sub-daily periods. The analysis at a half-hourly scale also considered three different orographic features (valley, flat and ridgetop), diverse climatic conditions (BSk, Csa, Cf and Df) and five categories related to rainfall intensity (light, moderate, intense, very intense and torrential). While IMERG_E and IMERG_L overestimate precipitation, IMERG_F reduces the error at all temporal scales. However, the calibration to which a Final run is subjected causes underestimation regardless in some areas, such as the Pyrenees mountains. The proportion of false alarms is a problem for IMERG, especially during the summer, mainly associated with the detection of false precipitation in the form of light rainfall. At sub-daily scales, IMERG showed high bias and very low correlation values, indicating the remaining challenge for satellite sensors to estimate precipitation at high temporal resolution. This behaviour was more evident in flat areas and cold semi-arid climates, wherein overestimates of more than 30% were found. In contrast, rainfall classified as very heavy and torrential showed significant underestimates, higher than 80%, reflecting the inability of IMERG to detect extreme sub-daily precipitation events.

<p>Satellite precipitation estimates (SPE) offer an excellent way to complement information on the spatio-temporal distribution of precipitation in semi-arid regions, such as Catalonia (NE Spain). The network of automatic weather stations of the Meteorological Service of Catalonia is used to evaluate the performance of the Integrated Multisatellite Estimates for GPM (IMERG). The semi-hourly scale analysis considered five categories related to precipitation intensity (light, moderate, heavy, very heavy, and torrential) and an analysis of two case studies of extreme precipitation was performed. Results found indicate that IMERG tends to overestimate light precipitation, while showing underestimates (errors above 60%) of cumulative precipitation in the rest of the intensity thresholds. This behaviour is related to the variability of precipitation on a point scale provided by the rain gauges and the uncertainties generated in the meshing process of the IMERG products. For high precipitation intensities, a time lag appears between satellite estimates and observations, related to the fact that the estimated precipitation may transform differently from the actual cloud movement. In addition, errors may be directly associated with the lack of information from the passive microwave (PMW) sensor. Finally, it is concluded that while IMERG can capture the spatio-temporal variability of the region in general, it has significant shortcomings in the detection of extreme sub-daily precipitation events. This research has been funded by projects WISE-PreP (RTI2018-098693-B-C32) and ARTEMIS (PID2021-124253OB-I00) and the Institute for Water Research (IdRA) of the University of Barcelona.</p>

<p>Within the framework of the GEWEX initiative  “Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment” (LIAISE), the WISE-PreP project was carried out to study precipitation processes aiming to characterize possible differences in precipitation induced by surface characteristics (irrigated vs non-irrigated areas) in NE Spain. Specific deployed instrumentation during the 2021 campaign included three sites equipped each with a vertical radar Doppler Micro Rain Radar (MRR) and a laser disdrometer (PARSIVEL), plus an additional PARSIVEL disdrometer, covering both irrigated and non-irrigated sites. Time series of vertical precipitation profiles and in-situ drop size distributions were recorded to study microphysical processes and related variables including precipitation intensity or convective vs stratiform rainfall regimes.</p> <p>First results show higher accumulated precipitation in the non-irrigated area (eastern area) than those in irrigated area (western area) in summer 2021, a feature also observed in summers for a previous reference period (2010-2019). Maximum and minimum daily temperatures were higher in irrigated areas than in non-irrigated areas. Both results are consistent with current climatology based on monthly precipitation and temperature that indicate the existence of a zonal gradient that increases semi-arid conditions (drier and warmer) from the east to the west. Disdrometer derived 1-min rainfall rate distributions presented some differences between the irrigated and non-irrigated areas during summer, unlike the other seasons when surface conditions are more similar in both areas. An overview of additional results obtained with numerical simulations using the WRF model is also provided. This research was supported by projects WISE-PreP (RTI2018-098693-B-C32) and ARTEMIS (PID2021-124253OB-I00) and the Water Research Institute (IdRA) of the University of Barcelona.</p>

<p>The LIAISE (Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment) field campaign was designed to study the effects of irrigation on a semi-arid area in NE Spain  (Boone et al. 2019). Within the framework of LIAISE, the WISE-PreP project was conceived to examine precipitation processes, on the one hand collecting high resolution data using Parsivel disdrometers and Micro-Rain Radars complementing operational rain-gauge and C-band Doppler weather radar observations and on the other one, carrying out numerical simulations to improve our understanding of physical processes involved. In this presentation we explore the irrigation impact on precipitation in Weather Research and Forecasting (WRF) model simulations during the intensive period of the LIAISE field campaign (15-30 July 2021). We quantify the precipitation accumulation and distribution by including the irrigation parameterization (Valmassoi et al 2020) and varying its parameters (days of irrigation, amount of irrigated water, hours of irrigation, etc.). First results indicate that fractional area of precipitation is greater if the irrigation parameterization is activated and if the irrigated amount is greater as well. Finally, we explore differences in stratiform vs convective fractions of precipitation. This work was partly funded by the project “Analysis of Precipitation Processes in the Eastern Ebro Subbasin” (WISE-PreP, RTI2018-098693-B-C32, MINECO/FEDER) and the Water Research Institute (IdRA) of the University of Barcelona.</p><p>References</p><p>Boone A, Best M, Cuxart J, Polcher J, Quintana P, Bellvert J, Brooke J, Canut-Rocafort G, Price J (2019). Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment (LIAISE). Gewex News, February 2019.</p><p>Valmassoi A, Dudhia J, Sabatino SD, Pilla F (2020). Evaluation of three new surface irrigation parameterizations in the WRF-ARW v3. 8.1 model: the Po Valley (Italy) case study. Geoscientific Model Development, 13(7), 3179-3201.</p>