Rosenfeld D., 1999: TRMM Observed First Direct Evidence of Smoke from Forest Fires Inhibiting Rainfall. Geophysical Research Letters. 26, (20), Tropical Rainfall Measuring Mission (TRMM) satellite observations show how rain is inhibited in clouds forming in dirty air, i.e., air containing many small CCN, contributed by aerosol particles such as smoke, air pollution and desert dust.

Ramanathan, V., P. J. Crutzen, J. T. Kiehl, and D. Rosenfeld, 2001: Aerosols, Climate and the Hydrological Cycle. Science, 294,

Small droplets follow the airflow streamlines and bypass the falling drop Large droplets collide with the falling drop

Smoke haze Visibility ~ 800 m N CN ~ cm -3 BC ~ 7  g m -3 Clear day Visibility ~ ??? km N CN ~ 500 cm -3 BC ~ 0.2  g m -3

Note the shallow precipitating clouds, extensive warm rainout, glaciation at T>-10 o C, and few lightning TRMM VIRS+PR, Amazon, :28 VIRS T-Re The “Green Ocean”: Maritime clouds over the Amazon

Smoke haze Visibility ~ 800 m N CN ~ cm -3 BC ~ 7  g m -3 Clear day Visibility ~ ??? km N CN ~ 500 cm -3 BC ~ 0.2  g m -3

VIRS+PR, Amazon, SEP 14:15 VIRS T-Re TOMS Aerosol Index 13 September 1998 Note that clouds do not precipitate before reaching height of 6.5 km or –12 o C isotherm, while containing ample cloud water. The “Green Ocean” turns dry: Smoky clouds over the Amazon

VIRS+PR, Amazon, :16 VIRS T-Re PR H-Z When the “smoky clouds” become Cb, they spark lightning and high Z

Deep Tropical clouds precipitate half the rainfall under conditions of suppressed coalescence, according to radar and aircraft measurements in Thailand (Rosenfeld and Woodley, 2001).

Disdrometer measured DSD of continental and maritime rainfall, as micophysically classified by VIRS overpass. The DSD is averaged for the rainfall during hours of the overpass time. The disdrometers are in Florida (Teflun B), Amazon (LBA), India (Madras) and Kwajalein. Application of TRMM Z-R shows a near unity bias in maritime clouds, but overestimates by a factor of 2 rainfall from continental clouds. Rosenfeld and Tokay, 2002

1. Swiss Locarno thunderstorms, continental (Joss and Waldvogel, 1970) Arizona mountain thunderstorms (Foote 1966) North Dakota, September Illinois thunderstorms, continental (Sims, 1964) Oklahoma thunderstorms, moderate continental (Petrocchi and Banis, 1980) Congo Squall line. Tropical continental (Sauvageot, 1994) PurtoRico thunderstorms. Coastal, moderate maritime (Ulbrich et al., 1999) Darwin Squalls. Coastal, tropical maritime (Maki et al., 2001) Darwin Convective DSD. Coastal, tropical maritime (Tokay et al., 1995) COARE Convective DSD. Equatorial maritime (Tokay and Short, 1996) Marshall Trade wind cumulus. Warm rain maritime (Stout and Mueller, 1968) Marshall Showers. Equatorial maritime. (Stout and Mueller, 1968) E. Equilibrium DSD Z-R relations for rainfall from maritime and continental convective clouds. The rain intensities for 40 and 50 dBZ are plotted in the figure. Note the systematic increase of R for a given Z for the transition from continental to maritime clouds.

53% of the atmospheric radiative loss is balanced by raditive gain. 47% of the atmospheric radiative loss is balanced by surface sensible (11%) and latent (36%) heat fluxes. What are the “Fluxes imposed changes” or “Thermodynamic imposed changes”? The term sounds unfamiliar, because we rarely considered manmade impacts on the fluxes, and most that we have done was driven by radiative considerations, with INDOEX as the major achievement.

“Tropical Rainfall Measuring Mission” was launched with the main objective to obtain the latent heat release as a major propellant of the global circulations. So why have we ignored until now the manmade imposed component? The answer: Because we had so little knowledge about the impact of anthropogenic aerosols on precipitation.

GCM simulation of the impact of biomass burning in the tropics on the global circulation in the extra-tropics. (Graf et al., 2000).

Trends in precipitation during the 20 th century shown on the right, compared with satellite observed aerosols shown below, for the northern winter season Note the general resemblances between areas with dense aerosols and decreasing trends of precipitation. The cause and effect relations remain to be determined. The aerosol index as obtained by POLDER on the ADEOS-I satellite (Duez et al., 2001) for the northern winter season. The aerosol index is the product of the size of the aerosols by their amounts, which is the parameter that is most relevant to the impact of the aerosol on cloud properties and precipitation. Trends (%/century) in December-February precipitation during (IPCC 2001). The numbers on the left ordinate are the averaged latitudinal trends.

Water Availability and Quality The Prime Environmental Problem of the 21 st Century The change of water resources is of the highest socio-economical impact of all climate change related issues. We get less rainfall for the same amount of clouds. The problem is worst in the most populated regions where the demand for water is greatest. Unlike greenhouse gases, these impacts are immediate (and reversible) at both local and global scales, affecting water resources and global circulation. So what can we do about it from space?

Ship Track Formation N~ 40 cm -3 W~ 0.30 g m -3 r e ~ 11.2 µm N~ 100 cm -3 W~ 0.75 g m -3 r e ~ 10.5 µm “Borrowed” from Michael King

First Indirect Effect Adding CCN makes clouds with more, smaller droplets. These clouds are whiter, reflect more sunlight  net cooling Ship tracks off the Washington coast

South Asian Haze: Seawifs Image; MARCH 21, 1999

Re > 15  m T Reff 15

Water Availability and Quality The Prime Environmental Problem of the 21 st Century The change of water resources is of the highest socio-economical impact of all climate change related issues. New insights about the ways mankind severely modifies rainfall at local and global scales. A comprehensive approach by: Observations from satellites, aircraft, radars and surface sampling Theoretical studies by numerical simulations Climatological studies

Suppression of Rain and Snow by Smoke and Air Pollution VIRS retrieved effective radius does not exceed the 14  m precipitation threshold in polluted clouds within area 2 in the Australia image. VIRS painting yellow pollution tracks in the clouds over South Australia, due to reduced droplets size. PR shows precipitation as white patches only outside the pollution tracks, although clouds have same depth. TMI shows ample water in the polluted clouds PR shows bright band in clean clouds. Therefore, pollution suppressed rain and snow in polluted clouds. This smoke stack of a mining complex well inland Canada causes the pollution track originating at the white asterisk Rosenfeld D., 1999: TRMM Observed First Direct Evidence of Smoke from Forest Fires Inhibiting Rainfall. Geophysical Research Letters. 26, (20), Rosenfeld D., 2000: Suppression of Rain and Snow by Urban and Industrial Air Pollution. Science, 287 (5459), Contact: Prof. Daniel Rosenfeld The Hebrew University of Jerusalem, Jerusalem 91904, Israel phone fax