Accounting for clouds in sea ice models

Abstract

Over sea ice in winter, the clouds, the surfacelayer air temperature, and the longwave radiation are closely coupled. This report uses archived data from the Russian North Pole (NP) drifting stations and recent data from Ice Station Weddell (ISW) to investigate this coupling. Both Arctic and Antarctic distributions of total cloud amount are U-shaped: that is, observed cloud amounts are typically either 0-2 tenths or 8-10 tenths in the polar regions. These data obey beta distributions; roughly 70 station-years of observations from the NP stations yielded fitting parameters for each winter month. Although surface-layer air temperature and total cloud amount are correlated, it is not straightforward to predict one from the other, because temperature is normally distributed while cloud amount has a U-shaped distribution. Nevertheless, the report presents a statistical algorithm that can predict total cloud amount in winter from surface-layer temperature alone and, as required, produces a distribution of cloud amounts that is U-shaped. Because sea ice models usually need cloud How to get copies of CRREL technical publications:

Importance of Clouds to the Decaying Trend and Decadal Variability in the Arctic Ice Cover.

“…As shown by Makshtas et al (1999), the summer trend is an increase in downward shortwave radiation, consistent with the decrease in low stratus clouds. Downward shortwave radiation increased by 19 W m À2 in June and July (Table 1).…”

“…As shown by the data collected at the Russian North Pole (NP) stations and archived at National Snow and Ice Data Center (National Snow and Ice Data Center 1996), Arctic cloud cover exhibits clear trends (Makshtas et al 1999). Although the NP program terminated after 1990, the trends up to this time are very significant, based on the 37-year long data.…”

Year on ice gives climate insights

“…A combination of radar and lidar was used effectively to monitor both cloud fraction and occurrence of liquid water in the cloud (Fig ure 3a).Though the Arctic Ocean is a desert, clouds were common at SHEBA. Makshtas et al [1999] report that Arctic clouds have a bimodal distribution: the sky is usually either clear (cloud amounts 0-1 tenths) or overcast (cloud amounts 9-10 tenths).The cloud frac tion reported by the lidar in Figure 3a can thus be interpreted as the fraction of the time that the sky is overcast.…”

High-Latitude Ocean and Sea Ice Surface Fluxes: Challenges for Climate Research

“…Surface downward LW fluxes at high latitudes have not been evaluated over the ocean but have been evaluated against land-based observations (e.g., König-Langlo and Augstein 1994; Key et al 1996;Guest 1998;Makshtas et al 1999) and are typically accurate to ~10-30 W m −2 at high latitudes at monthly time scales (Perovich et al 1999;Nussbaumer and Pinker 2012). For example, the parameterization of König-Langlo and Augstein (1994) reproduced the observations with root-mean-square (RMS) differences of <16 W m −2 .…”