AMIP I Diagnostic Subprojects: Further Information 

AMIP diagnostic subprojects are approved by the Working Group on Numerical Experimentation (WGNE) of the World Climate Research Programme (WCRP). A necessary condition for WGNE approval is the submission of a research proposal by prospective subproject leadership. Below are listed the current AMIP diagnostic subprojects, their leadership, and their objectives, as drawn from subproject proposals submitted to the WGNE. 

Table of Contents:


Subproject 1: Variability in the Tropics: Synoptic to Intraseasonal Timescales

Leadership

Julia Slingo, U.K. Universities Global Atmospheric Modelling Programme (UGAMP)
Ken Sperber, Program for Climate Model Diagnosis and Intercomparison (PCMDI)

Objectives

The aim of this subproject is to increase our understanding of the possible processes involved in the development, propagation and dissipation of synoptic waves and of the intraseasonal osciallation. This might be achieved by the intercomparison of these phenomena in a large number of models with diverse resolutions and physical parameterizations. A similar study (Park, C.-K., D.M. Straus, and K.-M. Lau, 1990: An evaluation of the structure of tropical intraseasonal oscillations in three general circulation models. J. Meteor. Soc. Japan, 68, 403-417) of the intraseasonal oscillation in three models suggests that the insight such an intercomparison might provide could be considerable.

Listed below are the primary questions which this subproject aims to address:

  • How does the intraseasonal oscillation depend on the mean vertical structure such as the static stability, shear of zonal wind component, diabatic heating?
  • Can we identify the characteristics of the convective parameterization, such as the vertical profile of the heating, the closure (e.g. moisture convergence), which might influence the existence of synoptic and intraseasonal variability? What is the role of the evaporation/wind feedback for both timescales?
  • Can the behavior of the intraseasonal oscillation be related to the incidence of synoptic variability, and/or vice versa?
  • What seasonal and interannual variability can we identify? How does it compare with reality? Can we learn something about the controlling factors (such as those identified in 1 and 2) from such a comparison?

Subproject 2: Intercomparison of Low Frequency Variability

Leadership

Francis W. Zwiers, Canadian Centre for Climate Modeling and Analysis (CCC)

Objectives

  • Diagnose and intercompare model bias
  • Partition interannual variability according to source (external forcing, internal dynamics, high frequency "weather noise")
  • Diagnose effects of external forcing
  • Intercompare interannual variability due to internal dynamics and "weather noise"
  • Diagnose potential predictability according to source (external forcing, internal dynamics)

Subproject 3: Cyclone Frequencies and Extratropical Intraseasonal Variability

Leadership

Steven Lambert, Canadian Centre for Climate Modeling and Analysis (CCC)

Objectives

The cyclone frequency climatology and its interannual variability will be extracted from each model and will be compared to observed climatologies. The following aspects will be examined; the total number of cyclone events for the extratropics of both hemispheres, their geographical distribution, the number of cyclone events as a function of central pressure, rates of intensification and rates of dissipation.

The second aspect of the diagnostic activity will examine each model's simulation of high frequency (2-10 day) transients, the intraseasonal (24-120 day) variability, and the forcing of the intraseasonal variability by the high frequency transients. The possible influence of the SSTs on intraseasonal variability will also be investigated.

 Using the results from the above, an attempt will be made to relate deficiencies in the simulated climatologies to formulations of the various models.

Subproject 4: Clear-sky Greenhouse Sensitivity, Water Vapor Distribution and Cloud Radiative Forcing

Leadership

J.P. Duvel and F. Cheruy, Laboratoire de Meteorologie Dynamique (LMD)

Objectives

The purpose is to use simple diagnostics to test the ability of the different models to reproduce the observed relations between the SST, the total precipitable water and the clear-sky outgoing longwave flux. We propose to test first these relations by using geographical distributions of these quantitites over ocean. The sensitivity of the greenhouse effect to the SST changes will be estimated by considering interannual changes.

Such analyses will give insight into the adequacy of parameterization schemes, such as the vertical diffusion and convective schemes, for representing the 3-D distribution of the water vapor. By inspecting the relation between the total precipitable water and the trapped thermal flux, the proposed diagnostics will also test some aspects of the radiative codes in clear-sky condition together with the vertical profiles of temperature and water vapor. The interannual sensitivity will test the ability of the different models to correctly redistribute the water vapor when the SST changes slightly from year to year.

Subproject 5: Surface Boundary Fluxes over the Oceans

Leadership

David A. Randall, Dept. of Atmospheric Science, Colorado State University (CSU)

Objectives

The purpose of this AMIP subproject is to investigate the implied ocean energy fluxes obtained from the surface energy budgets of the AMIP participants, to compare with observations from various sources, and to investigate reasons for discrepancies between the observations and the simulations.

Subproject 6: Monsoons

Leadership

T. N. Palmer, European Centre for Medium-Range Weather Forecasts (ECMWF)

Objectives

  • An investigation of the climatology of simulated monsoon circulations

  • An assessment of the ability of models to simulate observed interannual variations in monsoon activity
  • A study of the variability and predictability of interannual variations in the monsoons, and of simulated lagged teleconnections between seasonal monsoon variability and surface variables around the globe
The diagnosis is focussed on JJA, DJF to study the Asian/African and Australian regions respectively. However, it can be readily extended to study other areas.

Subproject 7: Intercomparison of Hydrologic Processes in General Circulation Models

Leadership

William K. M. Lau, Goddard Space Flight Center (GSFC)

Objectives

  • Provide an assessment of the ability of GCMs to represent regional and global distributions of rainfall in the context of the global hydrologic cycle

  • Evaluate the usefulness of GCM runoff in application to land hydrographic data.

Subproject 8: Polar Phenomena and Sea Ice

Leadership

John E. Walsh, University of Illinois at Urbana-Champaign (UIUC)

Objectives

Because of the importance of the ice/snow-albedo-temperature feedback, it is likely that the validity of the high-latitude amplification of surface temperature predicted by most greenhouse-warming simulations depends considerably on the accuracy with which snow cover and sea ice are simulated in the present climate. While sea ice is prescribed in the AMIP simulations, the high-latitude atmospheric fields that force sea ice dynamically and thermodynamically are likely to vary considerably from model to model. Similarly, the high-latitude fields that will interact with the subpolar ocean in coupled model simulations are likely to differ from model to model in physically important ways. The essence of our AMIP diagnostic subproject is a comparison and assessment of the simulated atmospheric fields that are the major drivers of sea ice and the high-latitude oceans. In the initial phase of the project, we are emphasizing the atmospheric fields that interact with the underlying surface. In a later phase, we will attempt to diagnose some of the model-to-model differences in the polar regions by examining the energy and moisture budgets of the model's high latitudes.

Subproject 9: Validation of High Latitude Tropospheric Circulation in the Southern Hemisphere

Leadership

Bryant J. McAvaney, Bureau of Meteorology Research Centre, (BMRC)

Objectives

  • Provide an assessment of the abilities of current state-of-the-art GCMs to simulate:
    • The semi-annual wave in zonal wind and sea level pressure at middle to high latitudes of the Southern Hemisphere.
    • The double jet-stream during the Austral winter.

  • Evaluate the mechanisms involved in maintaining the circulation at high latitudes of the Southern Hemisphere.
  • Investigate the simulated interannual variability in high latitude circulations.

Subproject 10: Diagnostics of Atmospheric Blocking in General Circulation Models

Leadership

Stefano Tilbaldi and Ennio Tosi, Atmospheric Dynamics Group of Bologna University (ADGB)

Objectives

It is proposed that diagnostics of blocking activity in both hemispheres be performed regularly on climate GCM outputs of the AMIP community. The objective of the subproject is to quantify and compare the ability of climate GCMs to represent blocking, which is one of the main sources of mid-latitude low-frequency variability. This should make a valuable contribution toward assessing the potential for applying various GCMs for regional studies, since the LFV generated by atmospheric blocking controls the regional redistribution of precipitation.

Subproject 11: Validation of Humidity, Moisture Fluxes, and Soil Moisture in General Circulation Models

Leadership

Alan Robock, University of Maryland
Dian Gaffen, NOAA Air Resources Laboratory
Richard D. Rosen, Atmospheric and Environmental Research, Inc.

Objectives

We will validate model output of three important components of the hydrological cycle: soil moisture, atmospheric humidity (including the vertical integral--precipitable water), and horizontal moisture fluxes. We will examine the climatology of the seasonal cycle as well as interannual variability of all these elements using unique observational data sets in our possession. In combination with the results of other diagnostic subproojects, we will contribute to a better understanding of the hydrological cycle of these models.

Subproject 12: Land-Surface Processes and Parameterizations (a joint AMIP-PILPS* project)

Leadership

Ann Henderson-Sellers, Climatic Impacts Centre (CIC)

Objectives

  • To compare the performance of participating PILPS models which are incorporated in AMIP GCMs
  • To generate atmospheric surface forcing from all AMIP GCMs with which to examine, off-line, a subset of PILPS* models

*PILPS - Project for the Intercomparison of Land-Surface Parameterization Schemes

Subproject 13: Diagnoses of Global Cloudiness Variations in General Circulation Model Results and Observational Data

Leadership

Igor I. Mokhov, Institute of Atmospheric Physics, Russian Academy of Sciences
Bryan C. Weare, Atmospheric Science Unit, University of California at Davis

Objectives

In order to develop more accurate model results of potential anthropogenic influences on climate a much better understanding of the role of clouds and cloud feedbacks in the present climate is required. Presently, there is considerable uncertainty concerning the intraannual and short-term interannual variations of monthly mean cloudiness and their relationship to basic atmospheric variables such as temperature and relative humidity. This proposed analysis will develop special diagnoses of observed cloudiness variability and interactions, evaluate the most important variations, and compare those observations with the general circulation model results.

Subproject 14: Cloud Radiative Forcing: Intercomparison and Validation

Leadership

Gerald L. Potter, Program for Climate Model Diagnosis and Intercomparison (PCMDI)
Anthony Slingo, Hadley Centre, U.K. Meteorological Office (UKMO)
Jean-Jacques Morcrette, European Centre for Medium-Range Weather Forecasts (ECMWF)

Objectives

The purpose of this subproject is to explore the use of ECMWF reanalysis products to obtain estimates of observed cloud radiative forcing (CRF) during the AMIP period (1979-1988), and to compare the results both with the AMIP models and with ERBE. Initially, simulations of the clear-sky longwave fluxes will be made, but if possible the simulations will be extended to cover shortwave fluxes. The experimental nature of this project will probably ensure that only a part of the calculations will be possible during the ECMWF reanalysis, necessitating the use of SAMPSON (Satellite using Operational Analysis--see Slingo and Webb, 1992 QJRMS) or similar off-line simulation systems.

Subproject 15: Atmospheric Angular Momentum in Global Numerical Models

Leadership

Raymond Hide, Jet Propulsion Laboratory, California Institute of Technology

Objectives

The Atmospheric Model Intercomparison Project (AMIP) of the World Climate Research Programme (WCRP) is one of the main activities of the WCRP's Working Group on Numerical Experimentation (WGNE), in its efforts to refine atmospheric models and improve their ability to produce useful forecasts of changes in weather and climate. As a possible contribution toward the achievement of this goal, the authors of this proposal would promote the thorough investigation of the extent to which the distribution of angular momentum and its exchange (a) between the atmosphere and the underlying planet, and (b) between different parts of the atmosphere, on timescales ranging from days to several years, can be represented correctly by the models being tested. The determination of the extent to which the distribution and exchange of angular momentum is represented correctly in global numerical models of the circulation of the atmosphere is clearly a matter of importance in the formulation of diagnostic schemes for assessing how well the models perform. It is readily shown that large errors in the treatment of energetic processes can be expected in simulations based on models that fail to represent atmospheric angular momentum (AAM) fluctuations satisfactorily.

Subproject 16: Simulations of the Stratospheric Circulation

Leadership

Carlos R. Mechoso, Dept. of Atmospheric Sciences, University of California at Los Angeles

Objectives

There are two major objectives in this subproject:
  • To determine the extent to which GCMs can stimulate the seasonal cycle in the stratosphere with emphasis on:
    • Formation and breakdown of the westerly vortex, including major warmings and interhemispheric differences in the evolution of final warmings.
    • Tropospheric-stratospheric connections in reference to planetary-wave behavior.
  • To analyze systematic differences in the behavior of planetary waves between models with different vertical resolutions.

Subproject 17: Multi-Scale Water and Energy Balance Processes and the GEWEX Continental-Scale International Project (GCIP)

Leadership

Donald Perkey, Institute for Global Change Reasearch and Education
Franklin Robertson, NASA/Marshall Space Flight Center (MSFC)

Objectives

The focus of this investigation is a multi-scale analysis of the moisture and energy cycling over North America using the AMIP GCM simulations, remotely-sensed data sets, and regional atmospheric models. Specifically, this collaborative effort will:
  • Examine the ability of AMIP GCM simulations to replicate low-frequency and transient linkages between North American regional water and energy balance and (i) remote SST forcing, (ii) in situ surface forcing within N.A. and, (iii) nonlinear dynamics generated internal to the atmosphere.
  • Investigate the ability of regional models nested within AMIP GCM boundary conditions to recover small-scale moisture transports, cloud structure, and surface energy flux (e.g. nocturnal low-level jet).
  • Employ regional models in assessing current global model capabilities to effectively represent the ensemble effects of subsynoptic moisture and heat transports, surface energy fluxes, cloud and radiative effects, and precipitation.

Subproject 18: Performance Capability of the Current Atmospheric General Circulation Models to Simulate Extreme Events and Associated Circulation Patterns

Leadership

Valentin P. Meleshko and A. V. Mesherskaya, Voeikov Main Geophysical Observatory (MGO)

Objectives

The goal of the project is evaluate performance capability of the GCMs in reproduction of extreme events such as intense cold and heat, and prolonged wet and dry spells and associated large-scale anomalies of the atmospheric circulation patterns which can be diagnosed directly from the models.

 The study will be based on use of observed and model simulated data sets for the 10-year AMIP period. It is intended to identify first observed persistent circulation anomalies with Hovmoeller diagrams constructed for particular regions of the northern hemisphere and the whole 10-year period. Similar diagrams will also be made for different &quotobserved" indices of extreme events over the same regions and the relationship between the latter and circulation patterns (troughs and ridges) will be defined using correlation analysis and distribution statistics (occurrence frequency, intensity, etc).

Subproject 19: Model Validation by Microwave Sounding Unit (MSU) Data

Leadership

John Christy, University of Alabama at Huntsville
Alan Robock, University of Maryland

Objectives

We will validate model output of surface and atmospheric temperature, the radiative energy balance at the top of the atmosphere, and by comparing the average output of the models with observations, attempt to identify signals of the causes of short-term climate changes during this period.

Subproject 20: Intercomparison of Model Simulated Atmospheric Circulation Features Related to Southern Africa

Leadership

Bruce C. Hewitson, University of Cape Town

Objectives

The objectives of the study are to validate and compare the GCMs with respect to particular atmospheric circulation features having bearing on the precipitation field; the temporal and spatial behavior of circulation features on the daily and monthly time scales, and the model internal consistency of cross-scale relationships between these features and the precipitation field with respect to the observed climate system.

Subproject 21: Surface Monthly and Daily Time-scale Climatologies and Regional Climate Anomalies

Leadership

Phil D. Jones, University of East Anglia

Objectives

This project will utilize the gridded observational datasets held in the Climatic Research Unit to evaluate the regional surface climate anomalies generated by the AMIP simulations over the period 1979-88. Four main aspects of regional surface climates will be addressed:
  • ENSO-related regional temperature and precipitation anomalies.
  • Regional-scale synoptic circulation.
  • Daily precipitation characteristics in the semi-arid tropics.
  • The diurnal temperature cycle over land areas.

Subproject 22: Comparative Energetics Analysis of Climate Models in the Wavenumber Domain

Leadership

Hiroshi L. Tanaka, Institute of Geoscience, University of Tsukuba
Akio Kitoh, Meteorological Research Institute of Japan

Objectives

The objectives of the proposed project are to evaluate the basic performance of present climate models with respect to the energy transfer and scale interaction in the wavenumber domain. Spectral energetics diagnosis will be performed for all climate model simulations by AMIP modeling groups. The energetics results will be compared with the observed atmosphere analyzed by the major operational analysis centers of the National Meteorological Center (NMC), European Center for Medium Range Weather Forecasts (ECMWF), and Japan Meteorological Agency (JMA).

First, spectral energy levels of model atmospheres will be compared with observations. The energy spectra will be calculated in the zonal wavenumber, meridional wavenumber, and vertical wavenumber domains. The model bias in the energy level will be analyzed.

Second, the magnitude and direction of the nonlinear wave-wave interactions will be examined for model atmospheres. The nonlinear energy transfer in the climate models will be compared with that of the operational weather forecast model.

Third, the variability in both the energy level and its interactions will be compared for the model atmosphere and observed atmosphere.

Subproject 23: Variations of the Centers of Action

Leadership

Sultan Hameed, State University of New York at Stony Brook (SUNY)
James Boyle and Benjamin Santer, Program for Climate Model Diagnosis and Intercomparison (PCMDI)

Objectives

Major modes of climate variability such as the Southern Oscillation, the North Atlantic Oscillation and the North Pacific Oscillation may be viewed as perturbations in the mean locations and intensities of a few atmospheric centers of action (COA). It follows that our understanding of interannual variability can be improved by diagnosing the simulated COA's in terms of model physical parameterizations. The aims of this proposed research are to investigate the morphology, the genesis and the variability of the major COAs in the tropical and northern Pacific and Atlantic oceans in several AMIP model simulations, to compare the model simulated COAs with observations, and to attempt to relate inter-model differences in the COA features in terms of the differences in model physical parameterizations and boundary conditions.

Subproject 24: Analysis of Caspian Sea Region Climate Data for 1979-1988 as Compared to AMIP Model Outputs

Leadership

G. S. Golitsyn, Institute for Atmospheric Physics (IAP) of the Russian Academy of Sciences

Objectives

The AMIP modeling groups have carried out simulations of world weather for 1979-1988 with prescribed SST. Two groups (MPI and NCAR) have expressed an interest in examining their integration results for a signal which may explain the observed rise in the level of the Caspian Sea during this decade. They have been supplied with observed data on monthly mean runoff, precipitation, evaporation and Kara-Bogaz-Gol (KBG) streamflow, and will compare their simulations with the observed data. 

Subproject 25: General Circulation Model Simulation of the East Asian Climate

Leadership

Wei-Chyung Wang, Atmospheric Sciences Research Center, State University of New York at Albany (SUNYA)

Objectives

  • To assess the ability of current GCMs to simulate East Asian Climate (EAC), including vacillations between high and low zonal index circulations, abrupt seasonal change in the atmospheric circulation and the east Asian monsoon.
  • To study the mechanisms and factors that caused the intraseasonal to interannual variability in the EAC, which include the dynamic and thermal effects of the Tibetan Plateau and anomalous surface boundary conditions (e.g., temperature,snow cover, soil moisture) over the Eurasian continent. Sensitivity experiments will be conducted to examine the individual mechanisms and factors.

Subproject 26: Monsoon Precipitation Simulation in the AMIP Runs

Leadership

Sulochana Gadgil, Centre for Atmospheric Sciences, Indian Institute of Science

Objectives

Monthly fields of precipitation and winds of the different models over the tropical belt (and particularly the monsoonal regions) will be intercompared with observations of rainfall (where available) and of satellite-derived measures of convection such as frequency of highly reflective clouds to ascertain the extent to which the following features are realistically simulated:
  • The spatial variation of the mean seasonal rainfall
  • The mean temporal patterns of the large-scale rainfall, duration of the rainy season etc.
  • The spatial structure of the interannual variation of the seasonal rainfall and the variation from one month to another within the same season
Models which simulate the decadal mean climatology and/or the intraannual and interannual variability sufficiently realistically for monsoonal regions (particularly South Asia and Africa) will be identified. Further diagnostic studies will be carried out to understand why some models (or versions) are able to simulate the precipitation associated with the continental tropical convergence zone while others are not; i.e. the sensitivity of the simulation of precipitation over monsoonal zones to resolution and physics will be examined.

UCRL-MI-122181