CHUVA

The physical process inside the clouds is one of the most unknown components of the weather and climate system. A description of the cloud processes through the use of standard meteorological parameters in numerical models has to be strongly improved to accurately describe the characteristics of hydrometeors, the latent heating profiles, the radiative balance, the air entrainment and the cloud updrafts and downdrafts. Numerical models have been improved to run at higher spatial resolutions where it is necessary to describe explicit these cloud processes. For instance, to analyze the effects of global warming in a given region is necessary to perform simulations considering all these cloud processes described above. Another important application that needs to have this knowledge is the precipitation estimation by satellite. The Brazilian space program is planning to launch, in 2014 a satellite to measure precipitation, which will be part of the GPM (Global Precipitation Measurement) constellation program. Warm clouds are responsible for a large amount of the precipitation in the tropics, especially in coastal regions. This cloud type is little studied and is not considered in satellite rainfall retrievals. This project will carry out field experiments at seven sites to investigate the different precipitation regimes in Brazil. To study these precipitation regimes, the field campaigns will make use of dual polarization radar, lidar, microwave radiometers, disdrometer, Radiosonde and various other instruments. The analysis will be performed considering the microphysical evolution and the cloud life cycle, the different precipitation estimation algorithms, the development of thunderstorms and lightning formation, the processes in the boundary layer and cloud microphysics modeling. This project intends to progress in the knowledge of the cloud processes to reduce the uncertainties in the precipitation estimation, mainly from warm clouds and consequently improving the knowledge of the water and energy budget and the cloud microphysics. This research project will carry studies on climate and physical processes by the means of conventional and special observations in order to create a database that can describe the cloud processes of the main precipitating system in Brazil. Accordingly, this proposal aims the development of a database that can be carried out to improve the remote sensing precipitation estimation thus validating and improving the cloud microphysical parameterization in the cloud models. This project will especially focus on the warm cloud precipitation produced by different types of convection.

This research project covers climate and physical processes studies using conventional and special observations (like polarimetric radar, radiometer, LIDAR, and several others instrumentations) to create a database describing the cloud processes of the main precipitating system in Brazil. It intends to create and exploit this database to improve remote sensing precipitation estimation, rainfall ground validation and microphysical parameterizations of the tri-dimensional characteristics of the precipitating clouds. This project will especially focus on the warm cloud precipitation produced by different types of convection (orography, cumulus congestus, CB initiation, stratus cumulus, life phase of the MCS). The Project proposes the collection of data regarding cloud processes, as being performed at different sites, ranging from middle latitude to tropical humid and semi arid regions.

Answer or improve the knowledge about the following basic questions and statement problems will be the foci of this project:

• How to estimate rainfall from warm clouds?

• What is the contribution of rain from warm clouds to the total precipitation in different regions of Brazil?

• How to improve both space and time precipitation estimation of rainfall over the continent for the GPM constellation?

• What are the average characteristics (3D - cloud processes) of the main regimes of precipitation in Brazil?

• What is the contribution of the aerosol in the process of formation of precipitation?

• What are the main surface and boundary layer processes in the formation and maintenance of clouds?

• How cloud microphysics and electrification processes evolves during the cloud life cycle?

• How to improve precipitation estimation and cloud microphysics description by using conventional and polarimetric radar?

Considering these statement problems the specific objectives are:

1. Gather data on the tri-dimensional structure of clouds in different regions of Brazil.

2. Build a data base of cloud properties including associated electrification features.

3. Build a data base of modeled structure of clouds, validated by observations in Brazil, for use on improvements in of algorithms for precipitation estimation.

4. Improve convective parameterizations of warm clouds and of cloud-aerosol interactions specifically for their impact on rainfall.

5. Assessment of the contribution of rain from warm clouds to the total precipitation in different regions of Brazil;

6. Study the mean characteristics of the main precipitation regimes in Brazil in terms of the cloud processes.

7. Study different methodologies to estimate precipitation from warm clouds.

8. Determine the thresholds of the onset of convection for liquid water and ice content;

9. Establish relationships between integrated ice content and precipitation as function of the cloud life stage;

10. Examine the differences between clouds processes for storms formed by different concentrations of aerosols.

11. Study the cloud life cycle from the microphysics point of view.

12. Compute the satellites rainfall estimation errors by different methodologies.

13. Study the minimum acceptable area for the integration of precipitation estimated by satellite?

14. Describe the temporal evolution of the electrical field during the thunderstorm development in conjunction with polarimetric variables, lightning discharges and their effects in the upper atmosphere signaled by Sprites and other Transient Luminous Events.

15. Depict the temporal evolution of the lightning activity, cloud area, surface rainfall and rainfall vertical structure.

16. Characterize the thunderstorms season over Brazil.

17. Characterize the atmosphere boundary layer for situations of the development of shallow and deeper clouds at different vegetation-climate regions.

18. Describe the typical atmosphere boundary layer for different cloud life cycles and cloud hydrometeor for different precipitation regimes.

19. Investigate the oscillation patterns of the integrated water vapor values in the periods that precede the events of strong storm.

20. Analyze how cloud processes occurs as function of distribution of turbulent fluxes, turbulent kinetic energy by using atmospheric modeling of heat and moisture transfer inside the Atmospheric Boundary Layer (ABL).