FIRE (First ISCCP Regional Experiment) is an ongoing multi-agency program designed to promote the development of improved cloud and radiation parameterizations for use in climate models, and to provide for assessment and improvement of International Satellite Cloud Climatology Program (ISCCP) products. The first five years of FIRE and ISCCP have yielded significant progress toward these objectives. 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. For the future, the relationship between clouds and climate has been identified as the top research priority for the U.S. Global Change Research Program. FIRE offers one of the best multidisciplinary strategies for addressing this research program.
FIRE is a multi-agency effort, enjoying support from the National Aeronautics and Space Administration (NASA), the National Science Foundation (NSF), the Office of Naval Research (ONR), the Department of Energy (DOE), the National Oceanic and Atmospheric Administration (NOAA), the United States Air Force (USAF), and other elements of the Department of Defense (DOD). Although FIRE is principally a United States national project, it benefits from important contributions by scientists from the United Kingdom and France.
The FIRE Science Team (FST) was organized in 1984 to define and implement a
coordinated research effort to investigate relationships between cloud systems
and climate and to verify and improve cloud monitoring techniques from
satellite platforms (Bretherton et al., 1983). The FST is composed of
scientists with modeling, experimental, and analysis skills for a diverse range
of disciplines. FIRE has undertaken tasks that are essential to understanding
cloud-climate relationships. The strategy of FIRE has been to combine modeling
activities with satellite, airborne, and surface observations to study two
types of climatically important cloud systems: cirrus and marine stratocumulus.
This strategy consists of three principal thrusts:
One of the reasons for the success of FIRE to date is the collection of a diverse group of scientific talent working toward an important, common goal. The FST contains all of the elements critical to making advances in the understanding of the relationships between clouds and climate. It is a diverse group of observationalists, analysts, and modelers from varied disciplines, acting with the support and encouragement of visionary administrators. They have melded themselves into a powerful scientific engine working on critical, unresolved issues in cloud-climate research, working productively together to a remarkable and perhaps unprecedented extent.
From its inception, FIRE has been designed to be conducted in two phases. FIRE
Phase I (1984-1989) was designed to address fundamental questions concerning
the maintenance of cirrus and marine stratocumulus cloud systems. Based on the
results of Phase I, including lessons learned in conducting intensive field
programs, FIRE Phase II (1989-1994) will focus on more detailed questions
concerning the formation, maintenance, and dissipation of these cloud systems.
Specifically, the scientific objectives of FIRE II, as outlined in the FIRE
Phase II Research Plan (1989), are to:
The first key component of FIRE II is a substantial modeling effort. The key to increasing our knowledge of climatically important cloud systems rests in the close coupling of future multi-scale modeling investigations with intensive data-gathering field programs. Models assist in the design of the field experiments, while observations provide initial conditions, physical process modules, and verification data for the models. Models provide a means to study nonlinear, interdependent processes; observations provide essential but only 'snapshot' independent views of important parameters. Large-scale models provide the necessary link to understanding the coupling between cloud-radiation processes and climate; observations represent the means of monitoring the climate and validating the models.
A second key component of FIRE II is a cirrus observational program scheduled for late fall 1991 in southeastern Kansas. A central question around which this investigation is designed is:
Are the cirrus cloud systems found in association with the polar/midlatitude and subtropical jet streams similar with respect to physical and radiative properties and evolution?
The location takes advantage of a newly deployed wind profiler network and offers the opportunity to extend FIRE cirrus investigations into the realm of the subtropical jet stream. The advent of new observation systems makes it possible to observe these upper tropospheric cloud systems in detail not possible only a few years ago.
Several specific questions which will be addressed using combined observational
and modeling approaches are:
In recognition of the true multi-scale control of cirrus cloud systems, the Phase II Cirrus Intensive Field Observations (IFO-II) will consist of a set of nested observations/platforms. The large-scale environment will be defined from NWS rawinsonde data extending from the west coast of the U.S. to the Mississippi river complemented by NWS gridded data and products and satellite data. The regional environs in the vicinity of the experiment will be monitored by special rawinsonde stations, the NWS wind profiler network, and satellites. The smaller scale will be intensely observed using special wind profiler installations, sophisticated surface-based lidar, radar and radiometry, and remote and in situ sensing from aircraft. Active participation by GCMs and mesoscale models will provide, for the first time, a methodology to investigate the links between the large-scale environment and the intensive, small-scale measurements.
In addition, the Pilot Tropical Cirrus Experiment (PTCE) will be conducted in the equatorial western Pacific to study the high and large cirrus cloud shields that pervade over the tropics due to intensive convective activity. The PTCE will be performed in January 1993 as part of the NASA ER-2 and DC-8 aircraft flights during the Tropical Ocean and Global Atmosphere/ Coupled Ocean-Atmosphere Experiment (TOGA/COARE). The PTCE is to be viewed as a target-of-opportunity experiment to take advantage of TOGA/COARE oceanic and atmospheric measurements and as a precursor to a possible FIRE Phase III research program to investigate convective-driven cirrus clouds.
A third key component of FIRE II is a major field experiment that is planned for the summer of 1992 in the eastern North Atlantic. The ASTEX (the Atlantic Stratocumulus Transition Experiment) observational program will be conducted in June 1992 from a base in the Azores and will consist of aircraft, island-based, ship-based, buoy, and satellite platforms. The surface-based sensors will include a number of sensing systems, such as Doppler cloud radar, wind profiler, sodar, passive microwave, rawinsonde, tethered balloon, and radiation instruments. This program has been designed to address a number of scientific questions that revolve around the following central, very complex question:
What are the consequences for the atmosphere and ocean of the prevalent boundary-layer cloud type and amount, and how are the cloud type and amount selected?
We have chosen to conduct ASTEX over the subtropical eastern North Atlantic Ocean during summer because in that region at that time of year there is a high probability of encountering a wide variety of boundary-layer cloud regimes that are easily accessible to observations from aircraft and island platforms, including the important broken cloud regimes. In contrast, the first boundary-layer cloud field campaign conducted by FIRE I encountered almost uniformly overcast conditions off the coast of Southern California.
A major goal of ASTEX is to provide data that can be used to drive and validate climate models. A key strategy is the measurement of the budgets of mass, thermodynamic energy, and moisture for an Eulerian 'grid column' located in the ASTEX observing region. Some of these observations are needed as inputs to climate model codes; good examples are the large-scale pressure gradient force, the large-scale vertical motion field, and the tendencies of temperature and moisture due to horizontal advection. A single-column version of a climate model can be used to simulate observed ASTEX cases, provided that such external forcings, which no single column model can determine, are provided as input. Obviously, additional ASTEX observations can be compared directly with results produced by a single-column climate model; examples are the cloudiness, the convective and radiative fluxes, and the vertical profiles of temperature and water vapor. In some cases, such observations can be used to test, decisively, the physical assumptions underlying the parameterizations used in a climate model. For example, models typically parameterize the entrainment rate in terms of the convective flux profiles; ASTEX will provide observations of both the flux profiles and the entrainment rate, allowing direct tests of such closure assumptions.
In addition, an Extended Time Observations (ETO) activity will consist of
coordinated satellite observations, meteorological analyses, and data from a
limited number of special ground sites with lidar and/or radiation measurements
throughout the year. These data will provide a means of extending the results
derived in the more detailed IFO intercomparison studies to larger time and
space scales. The ETO program will directly support the ISCCP and GCM
validation efforts.