An EarthCARE/ATLID simulator to evaluate cloud description in climate models

Abstract

International audienceClouds still remain the largest source of uncertainty in model-based predictions of future climate, thus the description of the clouds in climate models needs to be evaluated. In particular, the cloud detailed vertical distribution that impacts directly the cloud radiative effect needs to be evaluated. Active satellite sensors directly measure the cloud vertical distribution with high accuracy; their observations should be used for model evaluation together with a satellite simulator in order to allow fair comparison between models and observations. The next cloud lidar in space, EarthCARE/ATLID, is planned for launch in 2018, while the current spaceborne cloud lidar CALIPSO/CALIOP is expected to stop collecting data within the next coming years. Here we describe the characteristics of the ATLID lidar onboard the EarthCARE satellite (spatial resolution, SNR, wavelength, field of view, PRF, orbit, HSRL) that need to be taken into account to build a COSP/ATLID simulator. We then present the COSP/ATLID simulator, and the Low, Mid, High level cloud covers it produces, as well as the zonal mean cloud fraction profiles and the Height-intensity histograms that are simulated by COSP/ATLID when overflying an atmosphere predicted by LMDZ5 GCM. Finally, we compare the clouds simulated by COSP/ATLID with those simulated by COSP/CALIPSO when overflying the same atmosphere. As the main differences between ATLID and CALIOP are taken into account in the simulators, the differences between COSP/ATLID and COSP/CALIPSO clouds covers are less than 1% in night time condition

The Potential of a Multidecade Spaceborne Lidar Record to Constrain Cloud Feedback

“…As an example, Figure a shows this segmentation applied to the trend retrieved from a HadGEM2‐A realization of opaque cloud altitude in tropical deep convection conditions. We consider that the following missions will contribute the most to an extended spaceborne lidar record dedicated to the monitoring of changes in the global cloud distribution (Figure a): The CALIPSO mission (Winker et al, ), launched in 2006, source of the CALIPSO‐GOCCP data used to derive diagnostics (section 3) and expected to operate until 2018 at least, is at the time of writing the only cloud lidar in space operating continuously. The Earth‐CARE mission (Illingworth et al, ), expected to launch in 2020, will operate a 355‐nm lidar that will provide cloud detections reconcilable with CALIOP's (Reverdy et al, ). The MESCAL project is a spaceborne lidar project, currently in preliminary phase definition, to follow‐up CALIPSO and Earth‐CARE. Another unnamed mission in the far future to reach the spaceborne lidar record length necessary to detect climate‐related cloud trends. …”

“…2. The Earth-CARE mission (Illingworth et al, 2015), expected to launch in 2020, will operate a 355-nm lidar that will provide cloud detections reconcilable with CALIOP's (Reverdy et al, 2015).…”

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

“…For example, CloudSat radar (part of the A‐train) can detect a solid precipitation signature when the CALIPSO lidar gets attenuated [e.g., Mioche et al ., ; Zhang et al ., ]. In that regard, the results obtained here provide a good opportunity to help us prepare and assess the future EarthCARE multiinstrument mission [ Illingworth et al ., ; Reverdy et al ., ] (launch scheduled for 2018). This satellite will carry a polarized lidar and a radar sensitive to light precipitation that is expected to provide cloud and cloud phase measurements similar to the CALIPSO lidar and thus extend the lidar data set record.…”

The diurnal cycle of cloud profiles over land and ocean between 51° S and 51° N, seen by the CATS spaceborne lidar from the International Space Station

“…The diurnal cycle of clouds has been documented for decades by ground-based instruments (e.g., Gray and Jacobson, 1977) and geostationary satellites (e.g., Rossow, 1989). Even though climatologies give priority to how clouds change with seasons and geography, many studies noted the strong diurnal cycle of boundary layer clouds.…”