Simultaneous observations of an optical and an impact type disdrometer and their application in radar rainfall estimation are evaluated. The disdrometers and two collocated rain gauges were operated in the southwest Amazon region of Brazil in 1999 as part of a NASA Tropical Rainfall Measuring Mission (TRMM) field campaign and the hydro‐meteorological component of the Large Scale Biosphere–Atmosphere Experiment (LBA). During the experiment, we observed large drops with diameters greater than 5 mm. These large drops were not adequately detected by the impact disdrometer and resulted in differences in drop size distribution and integral rain parameters derived from the two sensors. Considering coincident observations, we calculated that the impact disdrometer recorded about 11% lower rainfall accumulations than the optical disdrometer. In addition, radar rainfall algorithms, which we derived from the impact and optical disdrometer measurements, showed instrument dependency. Out of four radar rainfall algorithms that we considered, rain rate derived from specific differential phase has the least dependency, while the rain rate derived from reflectivity at horizontal polarization and differential reflectivity combined exhibited the largest. We also observed the characteristics of rainfall and drop size distribution in two distinct wind regimes present during the TRMM–LBA field campaign. Rain was heavier in the easterly regime, with more large drops being present.

A statistical objective analysis (SOA) scheme is used to reanalyze the stage III estimate of rainfall, an hourly mosaic of digital precipitation arrays produced by a network of WSR-88Ds. The technique also uses rainfall measurements from the Oklahoma Mesonetwork that are taken over the Lake Altus area in southwest Oklahoma. The Lake Altus area is monitored by four WSR-88D radars: Frederick, Oklahoma; Twin Lakes, Oklahoma; Amarillo, Texas; and Lubbock, Texas. A total of 185 hourly maps of precipitation accumulation between June 1995 and July 1996 are used in the reanalysis. The results indicate that the stage III analysis underestimates total rainfall accumulations by as much as 40% when compared to the SOA reanalysis. Furthermore, the largest discrepancies between the stage III analysis and the SOA reanalysis coincide with overlapping areas of coverage between WSR-88D umbrellas. Some stage III precipitation fields used in this study clearly show fictitious high gradients of rainfall that exactly ... Abstract A statistical objective analysis (SOA) scheme is used to reanalyze the stage III estimate of rainfall, an hourly mosaic of digital precipitation arrays produced by a network of WSR-88Ds. The technique also uses rainfall measurements from the Oklahoma Mesonetwork that are taken over the Lake Altus area in southwest Oklahoma. The Lake Altus area is monitored by four WSR-88D radars: Frederick, Oklahoma; Twin Lakes, Oklahoma; Amarillo, Texas; and Lubbock, Texas. A total of 185 hourly maps of precipitation accumulation between June 1995 and July 1996 are used in the reanalysis. The results indicate that the stage III analysis underestimates total rainfall accumulations by as much as 40% when compared to the SOA reanalysis. Furthermore, the largest discrepancies between the stage III analysis and the SOA reanalysis coincide with overlapping areas of coverage between WSR-88D umbrellas. Some stage III precipitation fields used in this study clearly show fictitious high gradients of rainfall that exactly ...

Tempestades seguidas de enchentes e alagamentos em pontos da Região Metropolitana de São Paulo são eventos recorrentes nas estações chuvosas. O desempenho do modelo ARPS nas simulações numéricas de alta resolução espacial, para o evento de 04 de fevereiro de 2004, é avaliado por meio de erros estatísticos e índices de acurácia, com base no confronto entre a distribuição espacial da precipitação acumulada simulada e a estimada com o radar meteorológico de São Paulo. Os resultados quantificam a influência dos termos de advecção das equações primitivas nos erros de fase dos sistemas convectivos simulados, para o tipo de configuração atmosférica dominante no caso estudado. A assimilação incremental de medidas obtidas em estações de superfície durante a execução do modelo, corrige significativamente a fase das células convectivas profundas na região de influência das medidas, a qual é definida durante o processo de análise objetiva. Um novo índice de destreza para modelos de mesoescala é proposto (D PIELKE). As análises preliminares para o desempenho deste índice indicam adequação de sua formulação para o tipo de simulação efetuada.

The origin of modern disjunct plant distributions in the Brazilian Highlands with strong floristic affinities to distant montane rainforests of isolated mountaintops in the northeast and northern Amazonia and the Guyana Shield remains unknown. We tested the hypothesis that these unexplained biogeographical patterns reflect former ecosystem rearrangements sustained by widespread plant migrations possibly due to climatic patterns that are very dissimilar from present-day conditions. To address this issue, we mapped the presence of the montane arboreal taxa Araucaria, Podocarpus, Drimys, Hedyosmum, Ilex, Myrsine, Symplocos, and Weinmannia, and cool-adapted plants in the families Myrtaceae, Ericaceae, and Arecaceae (palms) in 29 palynological records during Heinrich Stadial 1 Event, encompassing a latitudinal range of 30°S to 0°S. In addition, Principal Component Analysis and Species Distribution Modelling were used to represent past and modern habitat suitability for Podocarpus and Araucaria. The data reveals two long-distance patterns of plant migration connecting south/southeast to northeastern Brazil and Amazonia with a third short route extending from one of them. Their paleofloristic compositions suggest a climatic scenario of abundant rainfall and relative lower continental surface temperatures, possibly intensified by the effects of polar air incursions forming cold fronts into the Brazilian Highlands. Although these taxa are sensitive to changes in temperature, the combined pollen and speleothems proxy data indicate that this montane rainforest expansion during Heinrich Stadial 1 Event was triggered mainly by a less seasonal rainfall regime from the subtropics to the equatorial region.