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Abstract. The development phase (DP) of the EUMETSAT Satellite Application Facility for Support to Operational Hydrology and Water Management (H-SAF) led to the design and implementation of several precipitation products, after 5 yr (2005)(2006)(2007)(2008)(2009)(2010) of activity. Presently, five precipitation estimation algorithms based on data from passive microwave and infrared sensors, on board geostationary and sun-synchronous platforms, function in operational mode at the H-SAF hosting institute to provide near real-time precipitation products at different spatial and temporal resolutions.In order to evaluate the precipitation product accuracy, a validation activity has been established since the beginning of the project. A Precipitation Product Validation Group (PPVG) works in parallel with the development of the estimation algorithms with two aims: to provide the algorithm developers with indications to refine algorithms and products, and to evaluate the error structure to be associated with the operational products.In this paper, the framework of the PPVG is presented: (a) the characteristics of the ground reference data available to H-SAF (i.e. radar and rain gauge networks), (b) the agreed upon validation strategy settled among the eight European countries participating in the PPVG, and (c) the steps of the validation procedures. The quality of the reference data is discussed, and the efforts for its improvement are outlined, with special emphasis on the definition of a ground radar Published by Copernicus Publications on behalf of the European Geosciences Union. S. Puca et al.:The validation service of the hydrological SAF geostationary products quality map and on the implementation of a suitable rain gauge interpolation algorithm. The work done during the H-SAF development phase has led the PPVG to converge into a common validation procedure among the members, taking advantage of the experience acquired by each one of them in the validation of H-SAF products. The methodology is presented here, indicating the main steps of the validation procedure (ground data quality control, spatial interpolation, upscaling of radar data vs. satellite grid, statistical score evaluation, case study analysis).Finally, an overview of the results is presented, focusing on the monthly statistical indicators, referred to the satellite product performances over different seasons and areas.

Previous works suggest that more El Niño-like conditions can be expected over the South American (SA) climate and atmospheric circulation because of the similarity of the predominately warm conditions in the sea surface temperature (SST) over the central-equatorial Pacific after the 1976/77 summer with those of the SSTs during El Niño events. Here, the summer (October to March) low-level atmospheric circulation over southern SA is studied in order to determine the specific changes that can be related with the global climate transition 1976/77. The rotated principal component analysis is applied to the daily 850-hPa geopotential height fields from the NCEP-NCAR reanalysis I for the periods before and after 1976/77. The second and third principal patterns reveal changes both in the order of explained variances and in some of their spatial features. They can be associated with an expansion of the subtropical South Atlantic anticyclone over SA and lower midlatitude cyclone activity after the 1976/77 summer. The latter is partly associated with the actual tendency toward the positive phase of the southern annular mode. The main patterns can even explain some changes in the observed precipitation over subtropical central-west Argentina as well as for other subtropical regions. Different inhomogeneity tests applied to the atmospheric circulation climatology support the changes. Results suggest that the atmospheric circulation change could be somewhat unique (not observed in the twentieth century) and, thus, it could not be thoroughly ascribed to the El Niño-like variability.

The relationship between the October (spring) total ozone column (TOC) midlatitude zonal asymmetry over the Southern Hemisphere (SH) and the stratospheric quasi-stationary wave 1 (QSW1) interannual phase variability is analyzed. Once contributions to the TOC from known global predictors, estimated with a multiregression model, are removed, the residual TOC interannual variability is observed to be dynamically coupled to the stratospheric QSW1 phase behavior. The stratospheric QSW1 interannual phase variability, when classified according to specifically designed indices, yields different circulation patterns in the troposphere and stratosphere. High (upper quartile) index values correspond to a westward rotation of the midlatitude ozone trough and the stratospheric QSW1 phase, while low (lower quartile) index values represent their eastwardrotated state. These values can be associated with statistically different tropospheric circulation patterns: a predominantly single poleward tropospheric jet structure for high index values and a predominantly double-jet structure for low index values. For the latter, there is a higher daily probability of double-jet occurrence in the troposphere and a stronger stratospheric jet. These jet structures and their daily behavior are supported by significant synoptic-scale activity anomalies over SH mid-to high latitudes as well as changes in tropospheric quasi-stationary waves 1-3. The wave activity flux (W flux) diagnosis shows the contribution of active quasistationary waves in the observed tropospheric anomalies associated with high and low index values. With low index values, the quasi-stationary waves lead to a self-sustaining state of the stratospheric-tropospheric coupled system. With high index values, the overall mid-to high latitude circulation is associated with wave energy propagation from the tropical central Pacific into higher latitudes. Thus, during the austral spring, there are interactions between the troposphere and stratosphere, leading to the locally well-defined upward and downward propagation of wave anomalies, that is, significant upper troposphere (UT)-lower stratosphere (LS) interactions can occur within a spring month itself.

The interannual-to-multidecadal variability of central-west Argentina (CWA) summer (October–March) precipitation and associated tropospheric circulation are studied in the period 1900–2010. Precipitation shows significant quasi cycles with periods of about 2, 4–5, 6–8, and 16–22 yr. The quasi-bidecadal oscillation is significant from the early 1910s until the mid-1970s and is present in pressure time series over the southwestern South Atlantic. According to the lower-frequency spectral variation, a prolonged wet spell is observed from 1973 to the early 2000s. The precipitation variability shows a reversal trend since then. In that wet epoch, the regionally averaged precipitation has been increased about 24%. The lower-frequency spectral variation is attributed to the climate shift of 1976/77. From the early twentieth century until the mid-1970s, the precipitation variability is associated with barotropic quasi-stationary wave (QSW) propagation from the tropical southern Indian Ocean and the South Pacific, generating vertical motion and moisture anomalies at middle-to-subtropical latitudes east of the Andes over southern South America. The QSW propagation could be related to anomalous convection partly induced by tropical anomalous SSTs in the western Indian Ocean (WIO). It could also be linked to another midlatitude source along the storm tracks, to the east of New Zealand. After 1976/77, the precipitation variability is associated with equatorial symmetric circulation anomalies linked to El Niño–Southern Oscillation (ENSO)-like warmer conditions. Positive moisture anomalies are consistently observed at lower latitudes in association with inflation of the western flank of the South Atlantic anticyclone. Outside of this, the precipitation variability is unrelated to ENSO.

This work focuses on the analysis of spatial and temporal variability of precipitation in the central region of southern Central Argentina (SCA), a climate transition area which has experienced an important agricultural expansion. For this purpose, gauge station precipitation datasets available in the area were extensively used. The annual cycle shows a defined dry season (May–August) and wet season (September–April). Wet season represents over 85% of annual totals. A regionalization analysis of wet‐season precipitation suggests five subregions with spatially homogeneous precipitation variability in SCA. Three out the five subregions are located in central SCA. Conveniently devised precipitation indices for the latter subregions show the presence of significant precipitation jumps by the early 1970s, and to a minor extent, the mid‐1960s. Precipitation jumps are responsible for the observed long‐term trends in central SCA, which explain positive precipitation changes over 30–40% of regional averages in the period 1922–2012. The presence of stationary and non‐stationary components in SCA precipitation variability remotely connects the region mainly with variations in equatorial Pacific SSTs. The assessment of greenhouse gases concentration effects on future projections of wet‐season precipitation over central SCA is investigated by means of multi‐model analysis of historical experiment, and the representative concentration pathways 4.5 (RCP 4.5) and 8.5 (RCP 8.5), provided by the Coupled Model Intercomparison Project Phase 5. Results suggest an overall increased precipitation, roughly 15% respect to present climate, under most severe future scenario.

Mendoza Province is the major Argentinian vitivinicultural region, and its grape production is fundamental for the national vintage. The 1979–2009 climate–annual grape yield relationships are analyzed, and total grape yield is shown to depend significantly on regional “summer” (October–March) precipitation. Precipitation negatively affects yields through plant disease and damage/destruction by hail. At interannual scales, summer regional precipitation variability can explains 25% of the yield variance. Summer precipitation modulates yield with a 6–8-yr period: wet (dry) summers can be associated with larger (smaller) grape damage/loss probability during the summer preceding the vintage, as well as lower (higher) grape yields in the subsequent annual campaign because of bud damage. With respect to monthly mean precipitation at Mendoza Observatory, wetter Novembers/Decembers can lead to lower yields. Hail during the summer of the previous harvest and during December could lower yields. Winter, late spring, and early summer mean maximum temperatures can impact current and subsequent annual yields: warmer (colder) months are linked to enhanced (decreased) yields. These relationships can be associated with circulation and SST conditions in the equatorial and extratropical Pacific Ocean basin and southern South America: SSTs within the southeastern South Pacific are related to western equatorial Pacific SSTs and convection, which modify circulation and water vapor transport over southern South America. Statistical multilinear modeling shows that the observed relationships among yield, precipitation, and temperature can explain at least 60% of the observed interannual yield variability. It is thus possible to quantitatively estimate, some months in advance, the upcoming vintage’s yield.

Westerlies are the main climatic feature in the mid-latitudes of the Southern Hemisphere (SH), driving the amount and distribution of precipitation. Patagonia is a vast region in South America's mid-latitudes, which encompasses 2 sub regions with highly distinct precipitation features. These two regions include wet Western Patagonia extending from the Pacific coast to the Andean highs (i.e. maximum elevations), and dry Eastern Patagonia situated leeward of the Andes in the Argentine steppe plains. Patagonia is influenced by strong mid-latitude westerlies throughout the year. Westerlies have been considered the unique driver of climate both in Western and Eastern Pata gonia. This research is focused on the Lago Cardiel catchment area in central Eastern Patagonia. A significant link between precipitation in that region and local zonal moisture transport from the Atlantic was established. A fraction of intense precipitation was related to strong local westward moisture transport, partly as a consequence of slow-moving weather systems crossing over Patagonia. As long as a dipolar pattern of long-term precipitation anomaly was observed between dry central Western/Southern Patagonia and wet central Eastern Patagonia, it could be interpreted as due to enhanced synoptic easterly moisture flux from the Atlantic. Thus, the westerlies rule was broken at least under blocking-like flows, which induced moist easterlies. The relatively wet 1940s exemplified this phenomenon. Such a conceptual framework can be applied to palaeoclimatic proxy record reconstructions as well as to general circulation model (GCM) outcomes for the late and mid-Holocene.