ISCCP and FIRE Phase I are research programs designed to start answering some of the questions about cloud-climate relationships. The first five years of these programs have yielded significant progress toward this objective. ISCCP has designed a methodology for monitoring cloudiness from space; this methodology has been employed to collect a near-global cloud climatology since 1983. This data set is now being used by scientists studying cloud and climate questions.
FIRE Phase I has made very significant contributions that have improved our understanding of the role of clouds in climate. FIRE has shown that clouds strongly influence the climate, and how these effects are produced. Our understanding of climatologically important cirrus and marine stratocumulus cloud systems has increased several-fold as a result of both measurement programs and modeling studies. FIRE Phase I research has produced undeniable quantitative evidence of the impact of cloud-radiation effects upon large scale circulation patterns, and moisture and precipitation distributions (Randall, 1989). FIRE Phase I research has assisted us in defining the limitations on the ISCCP data set imposed by time and space sampling criteria. Dramatic evidence of anthropogenic influences upon cloud radiative properties was simultaneously observed from satellites and in situ aircraft. Previously predicted influences of cloud geometry on cloud radiative properties were confirmed.
Phase I research results have yielded several very important results which will guide cirrus cloud system research in the years ahead. FIRE results have left little doubt that large-scale forcing is a dominant factor in the generation of extensive cirrus cloud systems in the middle latitudes (Starr anc Wylie, 1989). This is a very important result which lends strong support to parameterization potential in large scale models. The documentation of ever-present mesoscale structure in cirrus cloud systems has direct implications upon the maintenance and dissipation of these important cloud systems. The discovery of substantial numbers of ice crystals smaller than expected in most cirrus layers was made from a few direct samples of ice crystals and indirectly from radiation measurements from satellites and aircraft. While these small crystals represent only a small fraction of the ice/water content, they significantly alter the cirrus clouds' radiative properties and thus their impact on climate. Platt and Harshvardhan (1988), suggested a relationship between cirrus extinction and temperature. Analysis of FIRE data (midlatitude U.S.) and GATE data (tropical maritime) by Smith, et. al. (1989) suggest that this relationship may hold rather universally. This result holds dramatic implications for parameterizing cirrus cloud systems in large scale models. The Cirrus IFO revealed the pervasive layered structure of cirrus clouds. Most cirrus systems observed actually consisted of multiple layers although their bulk appearance was that of a single entity.
A complete description of FIRE-I results is given in Randall, et al, 1996. Individual
results are given in FIRE Science Results 1988
(NASA CP 3083, 1990) and FIRE Science Results 1989 (NASA CP 3079, 1990).