Cloud observations: the state of the art Alexander Chernokulsky A.M. Obukhov Institute of Atmospheric Physics Russian Academy of Sciences NABOS 2013 Ak. Fedorov, August 21 – September 22, 2013

Outline I.Cloudiness in the Earth climate system. II.A brief history of cloud observations and up- to-date cloudiness data. III.Cloud observations training on NABOS Alexander Chernokulsky Cloud observations: the state of the art

I. Cloudiness in the Earth climate system Alexander Chernokulsky Cloud observations: the state of the art

Two roles of cloudiness Cloudiness play two important roles in the Earth climate system: 1.Clouds are essential stages in the cycling of water between the earth and atmosphere. Clouds act both as sources and sinks of water vapor and in its turn water vapor is fundamental to the formation of clouds. 2.Clouds are a key component of the Earth radiation balance. The “ thermal absorbent ” character of water is greatly enhanced when in a condensed phase. On a molecule-by-molecule basis, water in either solid or liquid form in the atmosphere absorbs more than 1000 times more strongly than in gaseous form. So clouds contribute to the greenhouse effect. On the other hand, clouds reflect a fraction of the solar radiation that would otherwise be absorbed at the Earth’s surface. Alexander Chernokulsky Cloud observations: the state of the art

The global annual mean energy balance Alexander Chernokulsky Cloud observations: the state of the art Numbers indicate best estimates for the magnitudes of the globally averaged energy balance components together with their uncertainty ranges, representing present day climate conditions at the beginning of the twenty first century. Units W m -2. Wild et al., 2012

Cloud radiative forcing (effect) Alexander Chernokulsky Cloud observations: the state of the art Harrison et al., 1990; Stephens et al., 2012 Annual mean net (SW+LW) cloud radiative forcing Cloud radiative forcing (effect) can be estimated as the difference between clear-sky and total-sky fluxes (for LW and SW).

Cloud radiative forcing (effect) Alexander Chernokulsky Cloud observations: the state of the art Global annual mean shortwave cloud radiative forcing (so-called albedo effect of clouds): ± 0.3 W m -2 The main contributor to the SW CRF: stratus and strato-cumulus decks over eastern part of the oceans with high albedo (up to 70%) and small temperature contrast with the underlying surface (just 10ºC colder => small greenhouse effect) – potential for geoengineering + clouds in midlatitude stormtracks in summer hemisphere. Global annual mean longwave cloud radiative forcing (so-called greenhouse effect of clouds): 26.4 ± 0.4 W m -2 The main contributor to the LW CRF: high thin (subvisible) cirrus cloud decks in tropics with very cold tops. They transmit downward solar radiation without significant scattering or absorption, while blocking a larger fraction of the outgoing longwave radiation and reradiating it to space at very low temperatures.

Cloud radiative forcing (effect) Alexander Chernokulsky Cloud observations: the state of the art Global annual mean net cloud radiative forcing: ± 0.5 W m -2 So, globally, clouds cool the Earth (mostly by reflection of sunlight from clouds in the mid-latitude summer hemisphere). Regional values of cloud radiative forcing can reach W m -2 of both signs. Thus, clouds play an important role in the Earth climate system, they act in both global and regional scales. We should observe cloudiness with the accuracy.

II. A brief history of cloud observations and up-to-date cloudiness data. Alexander Chernokulsky Cloud observations: the state of the art

A history of cloud classifications Alexander Chernokulsky Cloud observations: the state of the art The first classification of clouds by naturalist J.-B. Lamark from France (he suggests 5 and after that 7 cloud types, but his classification had no spreading) Pharmaceutist Luke Howard from England invent Latin- based names for three main morphological type of clouds: Cirrus (means “feather”), cumulus (means “heap”) and stratus (means “layer”). His classification with some amendments (the major ones were proposed in 1887 by Hilderbrandson and Aber- Cromby) is used for now The first international cloud atlas with 30 color lithographs. 1930: the second edition of the international cloud atlas (75 photo pictures: from land and from planes); 1956: the third edition (101 photos) and so on s. Satellite cloud classification (not morphological, clouds divided by cloud optical thickness and cloud top pressure).

Morphological cloud classification Alexander Chernokulsky Cloud observations: the state of the art Nimbostratus Ns Stratus St Cumulus Cu Stratocumulus Cu Altocumulus Ac Cirrocumulus Cc Altostratus As Cirrostratus Cs Cirrus Ci Cumulonimbus Cb High-level clouds (H base >7-10 km, In the Arctic: H base >5 km) Middle-level clouds (H base >2 km, In the Arctic: H base >1.5 km) Low-level Clouds

Satellite cloud classification Alexander Chernokulsky Cloud observations: the state of the art Rossow and Schiffer, 1999

Cloud datasets Alexander Chernokulsky Cloud observations: the state of the art Cloud datasets Observations Surface-based Aerological Satellite Results of numerical simulations Reanalyses General circulation models From airplanes Meteorological radars Visual observations by observers Automated (sky-cameras etc.) Passive Active Combined

Annual zonal mean of total cloud fraction (TCF) SH NH Alexander Chernokulsky Cloud observations: the state of the art

Seasonal difference of zonal mean of TCF Zonal-mean difference of total cloud fraction between June-July- August and December-January-February Alexander Chernokulsky Cloud observations: the state of the art SH NH

Satellite observations Ground-based observations Reanalyses data GCM simulations Global annual mean of total cloud fraction Cloud fraction over the ocean Cloud fraction over land Cloud fraction over land and ocean over the ocean: ~0.7 (от 0.6 до 0.77) over land: ~0.55 (от 0.41 до 0.69) TCF according to observations: Over ocean and land: ~0.66 (от 0.56 до 0.75) Alexander Chernokulsky Cloud observations: the state of the art Chernokulsky, 2010

III. Cloud observations training on NABOS-2013 Alexander Chernokulsky Cloud observations: the state of the art

Why it is so important? Alexander Chernokulsky Cloud observations: the state of the art All meteorological observations from ships go to International archive and provide unique information about oceans’ weather (including clouds of course) Monthly means number of cloud observations (average for ).