CHASER: An Innovative Satellite Mission Concept to Measure the Effects of Aerosols on Clouds and Climate

Rennó, N. O.; Williams, Earle; Fischer, David G.; Fischer, Jürgen; Kremic, Tibor; Agrawal, Arun; Andreae, Meinrat O.; Bierbaum, Rosina; Blakeslee, Richard J.; Boerner, Anko; Bowles, Neil E.; Christian, H. J.; Cox, Ann; Dunion, Jason; Horváth, Ákos; Huang, Xianglei; Хаин, А.; Kinne, Stefan; Lemos, Maria Carmen; Penner, Joyce E.; Pöschl, Ulrich; Quaas, Johannes; Seran, Elena; Stevens, Björn; Walati, Thomas; Wagner, Thomas

doi:10.1175/bams-d-11-00239.1

Cited by 15 publications

(12 citation statements)

References 46 publications

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“…An alternative approach that can overcome these problems has been proposed, which in effect uses clouds as CCN counters [ Rosenfeld et al, ; Rennó et al, ]. In a laboratory CCN chamber, a set of known vapor supersaturations with respect to water is applied to an air sample containing aerosol.…”

Section: The Challenge and Methods Of Global Measurements Of Ccn And Inmentioning

confidence: 99%

“…To use naturally occurring clouds as CCN chambers, it is necessary to be able to retrieve the number of aerosol particles that nucleate into cloud drops at cloud base, N a , and the cloud‐base updraft, W b . A method for doing this from space was recently introduced by Rosenfeld et al [], and a satellite mission aimed at acquiring the necessary data was proposed [ Rennó et al, ].…”

Section: The Challenge and Methods Of Global Measurements Of Ccn And Inmentioning

confidence: 99%

“…This would allow disentangling the effects of aerosols from the effects of cloud‐base updraft, and thus meteorology, on boundary layer clouds. Measuring the updrafts at greater heights would require development of a suitable satellite, such as proposed by Rennó et al [].…”

Section: The Challenge and Methods Of Global Measurements Of Ccn And Inmentioning

confidence: 99%

“…Having simultaneous CCN, cloud microstructure and dynamical properties will make it possible to disentangle the aerosol and meteorological effects on the cloud systems. It would require a specially designed satellite, such as the instrument proposed by Rennó et al [].…”

Section: The Challenge Of Observing Cloud‐mediated Aerosol Radiative mentioning

confidence: 99%

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Global observations of aerosol-cloud-precipitation-climate interactions

et al. 2014

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Cloud drop condensation nuclei (CCN) and ice nuclei (IN) particles determine to a large extent cloud microstructure and, consequently, cloud albedo and the dynamic response of clouds to aerosol-induced changes to precipitation. This can modify the reflected solar radiation and the thermal radiation emitted to space. Measurements of tropospheric CCN and IN over large areas have not been possible and can be only roughly approximated from satellite-sensor-based estimates of optical properties of aerosols. Our lack of ability to measure both CCN and cloud updrafts precludes disentangling the effects of meteorology from those of aerosols and represents the largest component in our uncertainty in anthropogenic climate forcing. Ways to improve the retrieval accuracy include multiangle and multipolarimetric passive measurements of the optical signal and multispectral lidar polarimetric measurements. Indirect methods include proxies of trace gases, as retrieved by hyperspectral sensors. Perhaps the most promising emerging direction is retrieving the CCN properties by simultaneously retrieving convective cloud drop number concentrations and updraft speeds, which amounts to using clouds as natural CCN chambers. These satellite observations have to be constrained by in situ observations of aerosol-cloud-precipitation-climate (ACPC) interactions, which in turn constrain a hierarchy of model simulations of ACPC. Since the essence of a general circulation model is an accurate quantification of the energy and mass fluxes in all forms between the surface, atmosphere and outer space, a route to progress is proposed here in the form of a series of box flux closure experiments in the various climate regimes. A roadmap is provided for quantifying the ACPC interactions and thereby reducing the uncertainty in anthropogenic climate forcing.

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Section: The Challenge and Methods Of Global Measurements Of Ccn And Inmentioning

confidence: 99%

Section: The Challenge and Methods Of Global Measurements Of Ccn And Inmentioning

confidence: 99%

Section: The Challenge and Methods Of Global Measurements Of Ccn And Inmentioning

confidence: 99%

Section: The Challenge Of Observing Cloud‐mediated Aerosol Radiative mentioning

confidence: 99%

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Global observations of aerosol-cloud-precipitation-climate interactions

et al. 2014

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“…Disentangling the effects of aerosols and meteorology on cloud radiative effects is a major challenge that impedes us from quantifying the aerosol cloud‐mediated climate forcing and therefore constitutes the largest source of uncertainty in anthropogenic climate forcing [ Rosenfeld et al , ]. This disentanglement requires simultaneous measurements of cloud condensation nuclei (CCN) and cloud microphysical and dynamical properties from space, as envisioned by the CHASER (Clouds, Hazards, and Aerosols Survey for Earth Researchers) satellite mission [ Rosenfeld et al , ; Rennó et al , ]. The main idea of CHASER is using the base of convective clouds as CCN chambers.…”

Section: The Motivation For Satellite Retrievals Of Cloud Base Drop Cmentioning

confidence: 99%

Combined satellite and radar retrievals of drop concentration and CCN at convective cloud base

Fischman

Zheng

Goren

et al. 2014

Geophys. Res. Lett.

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The number of activated cloud condensation nuclei (CCN) into cloud drops at the base of convective clouds (N a ) is retrieved based on the high-resolution (375 m) satellite retrievals of vertical profiles of convective cloud drop effective radius (r e ). The maximum cloud base supersaturation (S) is calculated when N a is combined with radar-measured updraft and yields CCN(S), which was validated well against ground-based CCN measurements during the conditions of well-mixed boundary layer over the U.S. Department of Energy's Atmospheric System Research Southern Great Plains site. Satellite retrieving N a is a new capability, which is one essential component of simultaneous measurements of cloud microstructure and CCN from space by using clouds as natural CCN chambers. This has to be complemented by a methodology for satellite estimates of cloud base updraft, which is yet to be developed and demonstrated. In the mean time, the retrieved N a can be used for the assimilation of the combined CCN and updraft effects on clouds in models. The Motivation for Satellite Retrievals of Cloud Base Drop ConcentrationsDisentangling the effects of aerosols and meteorology on cloud radiative effects is a major challenge that impedes us from quantifying the aerosol cloud-mediated climate forcing and therefore constitutes the largest source of uncertainty in anthropogenic climate forcing . This disentanglement requires simultaneous measurements of cloud condensation nuclei (CCN) and cloud microphysical and dynamical properties from space, as envisioned by the CHASER (Clouds, Hazards, and Aerosols Survey for Earth Researchers) satellite mission Rennó et al., 2013]. The main idea of CHASER is using the base of convective clouds as CCN chambers. Measuring both the number concentrations of activated CCN into cloud drops at cloud base (N a ) and the updraft speed there (W b ) yields the vapor supersaturation (S) that the CCN particles are exposed to. Therefore, in fact, N a is the number concentration of CCN activated at S, i.e., CCN(S). This study represents a step toward the goal of satellite retrievals of CCN(S).Until now, satellite-retrieved cloud drop number concentrations (N d ) were based on vertically integrated cloud properties, such as liquid water path and optical depth [e.g., Szczodrak et al., 2001;Bennartz, 2007]. Therefore, the retrieved N d had to assume spatial homogeneity of the clouds, which is valid for layer much more than convective clouds. Furthermore, the mixing of the cloud with ambient air as it grows above its base dilutes N d to much smaller values than N a .Retrieving N a has become possible with the recent launch of the Suomi NPP (National Polar-Orbiting Partnership) satellite. The imager of the VIIRS (Visible Infrared Imaging Radiometer Suite) makes it possible by its breakthrough resolution of wave bands that allows retrieving cloud microstructure with the methodology that was developed by Rosenfeld et al. [2013]. The satellite resolution is 375 m at nadir, with little degradation across the swat...

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Satellite retrieval of convective cloud base temperature based on the NPP/VIIRS Imager

Zhu

Liu

et al. 2014

Geophysical Research Letters

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The advent of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-Orbiting Partnership (NPP) satellite provided a quantum jump in the satellite capabilities of retrieving cloud properties, because it nearly tripled the resolution in the thermal channels (375 m). This allowed us to develop a methodology for retrieving convective cloud base temperature (T b ) and validate it over the Atmospheric System Research Southern Great Plains site for the satellite early afternoon overpass time. The standard error of the T b retrieval was only 1.1°C. The knowledge of T b allows the calculation of cloud base height and the depth of the boundary layer, as well as the boundary layer water vapor mixing ratio with an accuracy of about 10%. The feasibility of retrieving cloud base temperature and height is an essential component that is required for retrieving cloud condensation nuclei (CCN) from satellites by using convective clouds as natural CCN chambers. The Motivation for Retrieving Cloud Base Temperature From SpaceA major challenge in our understanding the cloud-aerosol precipitation impacts on the climate system is the ability to retrieve from space the cloud condensation nuclei (CCN) supersaturation (S) spectra simultaneously with the cloud microstructure. Rosenfeld et al. [2012] proposed to use the convective clouds as natural CCN chambers and retrieved the cloud drop number concentrations (N d ) that were nucleated near cloud base along with cloud base updraft (w b ). Knowing both N d and w b allows the calculation of the supersaturation in cloud base. A satellite mission based on this principle was proposed by Rennó et al. [2013]. The satellite will retrieve both N d and w b for convective clouds that developed in the well-mixed boundary layer and calculate CCN(S) for individual clouds or small cloud clusters.The calculation of N d depends on the knowledge of cloud base temperature, T b , because the methodology is based in part on the calculated adiabatic cloud liquid water content as a function of height above cloud base [Freud et al., 2011]. Here we develop the methodology and show the feasibility to measure cloud base temperature from an existing satellite with a standard retrieval error of only 1.1°C.Although the main motivation for developing the methodology is for retrieving CCN from space, there are many other benefits for such a capability. The knowledge of cloud base temperature, when combined with meteorological data, allows the calculation of the height of this temperature and thus obtaining the height of the top of the boundary layer and the water vapor mixing ratio in it. This can be used for calculating more accurately the available convective potential energy and thus improving the prediction of convection and precipitation, especially in remote land areas where weather reports form the ground are scarce. Assimilating this information in numerical weather prediction models can improve the weather forecast and especially the quantitative precipitation predicti...

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CHASER: An Innovative Satellite Mission Concept to Measure the Effects of Aerosols on Clouds and Climate

Cited by 15 publications

References 46 publications

Global observations of aerosol-cloud-precipitation-climate interactions

Global observations of aerosol-cloud-precipitation-climate interactions

Combined satellite and radar retrievals of drop concentration and CCN at convective cloud base

Satellite retrieval of convective cloud base temperature based on the NPP/VIIRS Imager

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