D. M. Winker

The CALIPSO Mission: A Global 3D View of Aerosols and Clouds

Aerosols and clouds have important effects on Earths climate through their effects on the radiation budget and the cycling of water between the atmosphere and Earths surface. Limitations in our understanding of the global distribution and properties of aerosols and clouds are partly responsible for the current uncertainties in modeling the global climate system and predicting climate change. The CALIPSO satellite was developed as a joint project between NASA and the French space agency CNES to provide needed capabilities to observe aerosols and clouds from space. CALIPSO carries CALIOP, a two-wavelength, polarization-sensitive lidar, along with two passive sensors operating in the visible and thermal infrared spectral regions. CALIOP is the first lidar to provide long-term atmospheric measurements from Earths orbit. Its profiling and polarization capabilities offer unique measurement capabilities. Launched together with the CloudSat satellite in April 2006 and now flying in formation with the A-train satellite constellation, CALIPSO is now providing information on the distribution and properties of aerosols and clouds, which is fundamental to advancing our understanding and prediction of climate. This paper provides an overview of the CALIPSO mission and instruments, the data produced, and early results.

Assessment of Global Cloud Datasets from Satellites: Project and Database Initiated by the GEWEX Radiation Panel

Clouds cover about 70% of Earths surface and play a dominant role in the energy and water cycle of our planet. Only satellite observations provide a continuous survey of the state of the atmosphere over the entire globe and across the wide range of spatial and temporal scales that compose weather and climate variability. Satellite cloud data records now exceed more than 25 years; however, climate data records must be compiled from different satellite datasets and can exhibit systematic biases. Questions therefore arise as to the accuracy and limitations of the various sensors and retrieval methods. The Global Energy and Water Cycle Experiment (GEWEX) Cloud Assessment, initiated in 2005 by the GEWEX Radiation Panel (GEWEX Data and Assessment Panel since 2011), provides the first coordinated intercomparison of publicly available, standard global cloud products (gridded monthly statistics) retrieved from measurements of multispectral imagers (some with multiangle view and polarization capabilities), IR soun...

Laminar cirrus observed near the tropical tropopause by LITE

The Lidar In-space Technology Experiment (LITE) provided near-global observations of optically thin clouds during a 10-day Space Shuttle mission in September 1994. We report here on layers of cirrus occurring in thin sheets, which we refer to as ‘laminar’ cirrus, observed near the tropical tropopause. The layers were observed to have thicknesses generally between a few hundred meters and one kilometer and to be unusually homogeneous in the horizontal, with extents of up to 2700 km. Layers were observed near and possibly above the mean tropical tropopause, both in clear air and above intense tropical thunderstorms, but only in the tropics (35°N to 20°S). Thin layers near the tropopause were found to be common, but not pervasive, throughout the tropics including regions characterized by large scale subsidence in the middle troposphere.

Airborne lidar observations of the Pinatubo volcanic plume

A dual-polarization lidar aboard the NASA Electra aircraft was used in July 1991 to survey the stratospheric plume from the recent Mt. Pinatubo eruption. Many distinct layers were observed, ranging from 17 to 26 km in altitude. Peak scattering ratios of as high as 80 at 532 nm were recorded. Total particle mass of the plume 27 days after the eruption is estimated from these measurements to be on the order of 8 megatonnes, with perhaps half the original SO2 converted to aerosol at that point.

Combined lidar‐radar remote sensing: Initial results from CRYSTAL‐FACE

In the near future NASA plans to fly satellites carrying a multi-wavelength backscatter lidar and a 94-GHz cloud profiling radar in formation to provide complete global profiling of cloud and aerosol properties. The CRYSTAL-FACE field campaign, conducted during July 2002, provided the first high-altitude colocated measurements from lidar and cloud profiling radar to simulate these spaceborne sensors. The lidar and radar provide complementary measurements with varying degrees of measurement overlap. This paper presents initial results of the combined airborne lidar-radar measurements during CRYSTAL-FACE. The overlap of instrument sensitivity is presented, within the context of particular CRYSTAL-FACE conditions. Results are presented to quantify the portion of atmospheric profiles sensed independently by each instrument and the portion sensed simultaneously by the two instruments.

The Experimental Cloud Lidar Pilot Study (ECLIPS) for Cloud–Radiation Research

Abstract The Experimental Cloud Lidar Pilot Study (ECLIPS) was initiated to obtain statistics on cloud-base height, extinction, optical depth, cloud brokenness, and surface fluxes. Two observational phases have taken place, in October-December 1989 and April-July 1991, with intensive 30-day periods being selected within the two time intervals. Data are being archived at NASA Langley Research Center and, once there, are readily available to the international scientific community.

Preliminary analysis of observations of the Pinatubo volcanic plume with a polarization‐sensitive lidar

A dual-polarization lidar aboard the NASA Electra aircraft was used in July 1991 to survey the stratospheric plume from the recent Mt. Pinatubo eruption. Both depolarizing and non-depolarizing volcanic layers were observed, ranging from 17 to 26 km in altitude. Differences in the depolarization signatures of the layers indicates differences in the composition or physical state of the particles in the layers.

The CALIPSO mission and initial results from CALIOP

Satellite lidars are now beginning to provide new capabilities for global atmospheric sensing from space. Following the Lidar In-space Technology Experiment (LITE), which flew on the Space Shuttle in 1994, and the Geoscience Laser Altimeter System (GLAS), which launched in 2003, the CALIPSO satellite was launched on April 28, 2006. Carrying a two-wavelength polarization lidar along with two passive imagers, CALIPSO is now providing unique measurements to improve our understanding of the role of aerosols and clouds in the Earths climate system. The primary instrument on CALIPSO is CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization), a two-wavelength polarization lidar. Using a linearly polarized laser and a polarization-sensitive receiver, the instrument allows the discrimination of cloud ice/water phase and the identification of non-spherical aerosols. First light was achieved in June, 2006 and five months of nearly continuous observations have now been acquired. Initial performance assessments and calibration activities have been performed and instrument performance appears to be excellent. CALIPSO was developed within the framework of a collaboration between NASA and CNES.

Association of Antarctic polar stratospheric cloud formation on tropospheric cloud systems

[1] The formation of polar stratospheric clouds (PSCs) is critical to the development of polar ozone loss. However, the mechanisms of PSC formation remain poorly understood, which affects ozone loss models. Here, based on observations by the NASA A-train satellites, we show that 66% ± 16% and 52% ± 17% of PSCs over west and east Antarctica during the period June-October 2006 were associated with deep tropospheric cloud systems, with maximum depths exceeding 7 km. The development of such deep tropospheric cloud systems should cool the lower stratosphere through adiabatic and radiative processes, favoring PSC development. These deep systems also transport lower tropospheric air into the upper troposphere and lower stratosphere. These new findings suggest that Antarctic PSC formation is closely connected to tropospheric meteorology and thus governed by synoptic scale dynamics, local topography, and large-scale circulation. More dedicated studies are still needed to better understand Antarctic PSC formation.

Using in-situ airborne measurements to evaluate three cloud phase products derived from CALIPSO

We compare the cloud detection and cloud phase determination of three independent climatologies based on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) to airborne in situ measurements. Our analysis of the cloud detection shows that the differences between the satellite and in situ measurements mainly arise from three factors. First, averaging CALIPSO Level l data along track before cloud detection increases the estimate of high- and low-level cloud fractions. Second, the vertical averaging of Level 1 data before cloud detection tends to artificially increase the cloud vertical extent. Third, the differences in classification of fully attenuated pixels among the CALIPSO climatologies lead to differences in the low-level Arctic cloud fractions. In another section, we compare the cloudy pixels detected by colocated in situ and satellite observations to study the cloud phase determination. At midlatitudes, retrievals of homogeneous high ice clouds by CALIPSO data sets are very robust (more than 94.6% of agreement with in situ). In the Arctic, where the cloud phase vertical variability is larger within a 480 m pixel, all climatologies show disagreements with the in situ measurements and CALIPSO-General Circulation Models-Oriented Cloud Product (GOCCP) report significant undefined-phase clouds, which likely correspond to mixed-phase clouds. In all CALIPSO products, the phase determination is dominated by the cloud top phase. Finally, we use global statistics to demonstrate that main differences between the CALIPSO cloud phase products stem from the cloud detection (horizontal averaging, fully attenuated pixels) rather than the cloud phase determination procedures.