CHUVA, meaning “rain” in Portuguese, is the acronym for the Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud-Resolving Modeling and to the Global Precipitation Measurement (GPM). The CHUVA project has conducted five field campaigns; the sixth and last campaign will be held in Manaus in 2014. The primary scientific objective of CHUVA is to contribute to the understanding of cloud processes, which represent one of the least understood components of the weather and climate system. The five CHUVA campaigns were designed to investigate specific tropical weather regimes. The first two experiments, in Alcantara and Fortaleza in northeastern Brazil, focused on warm clouds. The third campaign, which was conducted in Belém, was dedicated to tropical squall lines that often form along the sea-breeze front. The fourth campaign was in the Vale do Paraiba of southeastern Brazil, which is a region with intense lightning activity. In addition to contributing to the understanding of cloud process evolution from storms to thunderstorms, this fourth campaign also provided a high-fidelity total lightning proxy dataset for the NOAA Geostationary Operational Environmental Satellite (GOES)-R program. The fifth campaign was carried out in Santa Maria, in southern Brazil, a region of intense hailstorms associated with frequent mesoscale convective complexes. This campaign employed a multimodel high-resolution ensemble experiment. The data collected from contrasting precipitation regimes in tropical continental regions allow the various cloud processes in diverse environments to be compared. Some examples of these previous experiments are presented to illustrate the variability of convection across the tropics.

Since the successful launch of the Tropical Rainfall Measuring Mission (TRMM) satellite, measurements of a wide variety of precipitating systems have been obtained with unprecedented detail from the first space-based radar [precipitation radar (PR)]. In this research, a methodology is developed that matches coincident PR and ground-based volume scanning weather radar observations in a common earth parallel three-dimensional Cartesian grid. The data matching is performed in a way that minimizes uncertainties associated with the type of weather seen by the radars, grid resolution, and differences in radar sensitivities, sampling volumes, viewing angles, and radar frequencies. The authors present comparisons of reflectivity observations from the PR and several U.S. weather surveillance Doppler radars (WSR-88D) as well as research radars from the TRMM field campaigns in Kwajalein Atoll and the Large Biosphere Atmospheric (LBA) Experiment. Correlation values above 0.8 are determined between PR and gro... Abstract Since the successful launch of the Tropical Rainfall Measuring Mission (TRMM) satellite, measurements of a wide variety of precipitating systems have been obtained with unprecedented detail from the first space-based radar [precipitation radar (PR)]. In this research, a methodology is developed that matches coincident PR and ground-based volume scanning weather radar observations in a common earth parallel three-dimensional Cartesian grid. The data matching is performed in a way that minimizes uncertainties associated with the type of weather seen by the radars, grid resolution, and differences in radar sensitivities, sampling volumes, viewing angles, and radar frequencies. The authors present comparisons of reflectivity observations from the PR and several U.S. weather surveillance Doppler radars (WSR-88D) as well as research radars from the TRMM field campaigns in Kwajalein Atoll and the Large Biosphere Atmospheric (LBA) Experiment. Correlation values above 0.8 are determined between PR and gro...

An objective tracking of mesoscale convective systems (MCSs) observed in full‐resolution Geostationary Operational Environmental Satellite (GOES) satellite images has been applied during the Wet Season Atmospheric Mesoscale Campaign/Large‐Scale Biosphere–Atmosphere (WETAMC/LBA) experiment in Amazonia from January to February 1999 to document the characteristics of the convective cloud organization in the southwestern Amazon region. The same tracking methodology was also applied to the National Aeronautical Space Administration (NASA) Tropical Ocean Global Atmosphere (TOGA) C‐Band radar data in order to estimate the propagation of the convective rain cells from constant altitude plan position indicators (CAPPI) at a height of 2 km. The convective activity showed two different patterns named Easterly and Westerly regimes according to the wind flow in the 700–850‐hPa layer. During the Easterly regime, MCSs and rain cells had closely related propagations. MCS as well as rain cell propagations were associated mostly to the midlevel mean flow. During the Westerly regime, the propagations of both MCSs and rain cells were much more disorganized, there was no clear relationship with the mean atmospheric flow at any level, although the rain cells have a slight tendency to propagate eastward, and the low‐level rain cells propagated quite independently of the high‐level cloud cover. MCS initiations were mostly driven by topography, that is, high escarpment and relatively high elevation.

Measurements of cloud condensation nuclei (CCN), aerosol size distribution and non-refractory chemical composition were performed from 16 to 31 October 2012 in the São Paulo Metropolitan Area (SPMA), Brazil. CCN measurements were performed at 0.23, 0.45, 0.68, 0.90 and 1.13% water supersaturation and were subsequently compared with the Köhler theory, considering the chemical composition. Real-time chemical composition has been obtained by deploying, for the first time in the SPMA, an aerosol chemical ionization monitor (ACSM). CCN closure analyses were performed considering internal mixtures. Average aerosol composition during the studied period yielded (arithmetic mean~± standard deviation) 4.81 ± 3.05, 3.26 ± 2.10, 0.30 ± 0.27, 0.52 ± 0.32, 0.37 ± 0.21 and 0.04 ± 0.04 μg m−3 for organics, BC, NH4, SO4, NO3 and Cl, respectively. Particle number concentration was 12 813 ± 5350 cm−3, with a dominant nucleation mode. CCN concentrations were on average 1090 ± 328 and 3570 ± 1695 cm−3 at SS = 0.23% and SS = 1.13%, respectively. Results show an increase in aerosol hygroscopicity in the afternoon as a result of aerosol photochemical processing, leading to an enhancement of both organic and inorganic secondary aerosols in the atmosphere, as well as an increase in aerosol average diameter. Considering the bulk composition alone, observed CCN concentrations were substantially overpredicted when compared with the Köhler theory (44.1 ± 47.9% at 0.23% supersaturation and 91.4 ± 40.3% at 1.13% supersaturation). Overall, the impact of composition on the calculated CCN concentration (NCCN) decreases with decreasing supersaturation, partially because using bulk composition introduces less bias for large diameters and lower critical supersaturations, defined as the supersaturation at which the cloud droplet activation will take place. Results suggest that the consideration of only inorganic fraction improves the calculated NCCN. Introducing a size-dependent chemical composition based on filter measurements from previous campaigns has considerably improved simulated values for NCCN (average overprediction error 14.8 ± 38.6% at 0.23% supersaturation and 3.6 ± 21.6% at 1.13% supersaturation). This study provides the first insight on aerosol real-time composition and hygroscopicity at a site strongly impacted by emissions of a unique vehicular fleet due to the extensive biofuel usage.