Abstract. Clouds play an important role in the climate system: (1) cooling Earth
by reflecting incoming sunlight to space and (2) warming Earth by
reducing thermal energy loss to space. Cloud radiative effects are
especially important in polar regions and have the potential to
significantly alter the impact of sea ice decline on the surface radiation
budget. Using CERES (Clouds and the Earth's Radiant Energy System) data and 32 CMIP5 (Coupled Model Intercomparison Project) climate models, we quantify the
influence of polar clouds on the radiative impact of polar sea ice
variability. Our results show that the cloud short-wave cooling effect
strongly influences the impact of sea ice variability on the surface
radiation budget and does so in a counter-intuitive manner over the polar
seas: years with less sea ice and a larger net surface radiative flux show a
more negative cloud radiative effect. Our results indicate that 66±2%
of this change in the net cloud radiative effect is due to the reduction in
surface albedo and that the remaining 34±1 % is due to an increase in cloud
cover and optical thickness. The overall cloud radiative damping effect is
56±2 % over the Antarctic and 47±3 % over the Arctic. Thus,
present-day cloud properties significantly reduce the net radiative impact
of sea ice loss on the Arctic and Antarctic surface radiation budgets. As a
result, climate models must accurately represent present-day polar cloud
properties in order to capture the surface radiation budget impact of polar sea ice loss and thus the surface albedo feedback.
Abstract. The surface radiation budget of the Arctic Ocean plays a central
role in summer ice melt and is governed by clouds and surface albedo. I
calculated the net radiation flux for a range of albedos under sunny and
cloudy skies and determined the break-even value, where the net radiation is
the same for cloudy and sunny skies. Break-even albedos range from 0.30 in
September to 0.58 in July. For snow-covered or bare ice, sunny skies always
result in less radiative heat input. In contrast, leads always have, and
ponds usually have, more radiative input under sunny skies than cloudy
skies. Snow-covered ice has a net radiation flux that is negative or near
zero under sunny skies, resulting in radiative cooling. Areally averaged
albedos for sea ice in July result in a smaller net radiation flux under
cloudy skies. For May, June, August, and September, the net radiation is
smaller under sunny skies.
Abstract
Measurements of the long- and shortwave incident radiation taken from the USCGC Polar Sea during a research cruise to the Northeast Water Polynya during the summer of 1993 are analyzed together with observations of cloud type and amount to determine the effects of summertime Arctic clouds on the surface radiation budget. It is found that the solar zenith angle is critical in determining whether clouds heat or cool the surface. For large solar zenith angles (>∼80°) the infrared heating effect of clouds is greater than the reduction in insolation caused by clouds, and the surface is heated by the presence of cloud. For smaller zenith angles, cloud cover cools the surface, and for intermediate zenith angles, the surface radiation budget is insensitive to the presence of, or changes in, cloud cover.
Abstract. The second edition of the satellite-derived climate data record CLARA (The CM SAF Cloud, Albedo And Surface Radiation dataset from AVHRR data – second edition denoted as CLARA-A2) is described. The data record covers the 34-year period from 1982 until 2015 and consists of cloud, surface albedo and surface radiation budget products derived from the AVHRR (Advanced Very High Resolution Radiometer) sensor carried by polar-orbiting, operational meteorological satellites. The data record is produced by the EUMETSAT Climate Monitoring Satellite Application Facility (CM SAF) project as part of the operational ground segment. Its upgraded content and methodology improvements since edition 1 are described in detail, as are some major validation results. Some of the main improvements to the data record come from a major effort in cleaning and homogenizing the basic AVHRR level-1 radiance record and a systematic use of CALIPSO-CALIOP cloud information for development and validation purposes. Examples of applications studying decadal changes in Arctic summer surface albedo and cloud conditions are provided.
Abstract
Recently developed system for assessment of radiation budget for the Baltic Sea has been presented and verified. The system utilizes data from various sources: satellite, model and in situ measurements. It has been developed within the SatBałtyk project (Satellite Monitoring of the Baltic Sea Environment - www.satbaltyk.eu) where the energy radiation budget is one of the key element. The SatBałtyk system generates daily maps of the all components of radiation budget on every day basis. We show the scheme of making daily maps, applied algorithms and empirical data collection within the system. An empirical verification of the system has been carried out based on empirical data collected on the oil rig placed on the Baltic Sea. This verification concerned all the components of the surface radiation budget. The average daily NET products are estimated with statistical error ca. 13 Wm-2. The biggest absolute statistical error is for LWd component and equals 14 Wm-2. The relative error in relation to the average annual values for whole Baltic is the biggest for SWu and reaches 25%. All estimated components have correlation coefficient above 0.91.
Clouds damp the radiative impacts of polar sea ice loss