Cloud Microphysical Properties based on Airborne In Situ Observations and Evaluation of a Weather Forecasting Model and a Global Climate Model

AbstractCloud ice microphysical properties measured or estimated from in situ aircraft observations are compared with global climate models and satellite active remote sensor retrievals. Two large datasets, with direct measurements of the ice water content (IWC) and encompassing data from polar to tropical regions, are combined to yield a large database of in situ measurements. The intention of this study is to identify strengths and weaknesses of the various methods used to derive ice cloud microphysical properties. The in situ data are measured with total water hygrometers, condensed water probes, and particle spectrometers. Data from polar, midlatitude, and tropical locations are included. The satellite data are retrieved from CloudSat/CALIPSO [the CloudSat Ice Cloud Property Product (2C-ICE) and 2C-SNOW-PROFILE] and Global Precipitation Measurement (GPM) Level2A. Although the 2C-ICE retrieval is for IWC, a method to use the IWC to get snowfall rates S is developed. The GPM retrievals are for snowfall rate only. Model results are derived using the Community Atmosphere Model (CAM5) and the Met Office Unified Model [Global Atmosphere 7 (GA7)]. The retrievals and model results are related to the in situ observations using temperature and are partitioned by geographical region. Specific variables compared between the in situ observations, models, and retrievals are the IWC and S. Satellite-retrieved IWCs are reasonably close in value to the in situ observations, whereas the models’ values are relatively low by comparison. Differences between the in situ IWCs and those from the other methods are compounded when S is considered, leading to model snowfall rates that are considerably lower than those derived from the in situ data. Anomalous trends with temperature are noted in some instances.

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Constraining the model representation of the aerosol life cycle in relation to sources and sinks.

10.5194/egusphere-egu2020-21948 ◽

2020 ◽

Author(s):

Paul Kim ◽

Daniel Partridge ◽

James Haywood

Keyword(s):

Climate Change ◽

Life Cycle ◽

Large Scale ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Evaluation Framework ◽

Microphysical Properties ◽

The Impact ◽

Source And Sink

Global climate model (GCM) ensembles still produce a significant spread of estimates for the future of climate change which hinders our ability to influence policymakers. The range of these estimates can only partly be explained by structural differences and varying choice of parameterisation schemes between GCMs. GCM representation of cloud and aerosol processes, more specifically aerosol microphysical properties, remain a key source of uncertainty contributing to the wide spread of climate change estimates. The radiative effect of aerosol is directly linked to the microphysical properties and these are in turn controlled by aerosol source and sink processes during transport as well as meteorological conditions.A Lagrangian, trajectory-based GCM evaluation framework, using spatially and temporally collocated aerosol diagnostics, has been applied to over a dozen GCMs via the AeroCom initiative. This framework is designed to isolate the source and sink processes that occur during the aerosol life cycle in order to improve the understanding of the impact of these processes on the simulated aerosol burden. Measurement station observations linked to reanalysis trajectories are then used to evaluate each GCM with respect to a quasi-observational standard to assess GCM skill. The AeroCom trajectory experiment specifies strict guidelines for modelling groups; all simulations have wind fields nudged to ERA-Interim reanalysis and all simulations use emissions from the same inventories. This ensures that the discrepancies between GCM parameterisations are emphasised and differences due to large scale transport patterns, emissions and other external factors are minimised.Preliminary results from the AeroCom trajectory experiment will be presented and discussed, some of which are summarised now. A comparison of GCM aerosol particle number size distributions against observations made by measurement stations in different environments will be shown, highlighting the difficulties that GCMs have at reproducing observed aerosol concentrations across all size ranges in pristine environments. The impact of precipitation during transport on aerosol microphysical properties in each GCM will be shown and the implications this has on resulting aerosol forcing estimates will be discussed. Results demonstrating the trajectory collocation framework will highlight its ability to give more accurate estimates of the key aerosol sources in GCMs and the importance of these sources in influencing modelled aerosol-cloud effects. In summary, it will be shown that this analysis approach enables us to better understand the drivers behind inter-model and model-observation discrepancies.

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A Mathematical Framework for Analysis of Water Tracers. Part II: Understanding Large-Scale Perturbations in the Hydrological Cycle due to CO2 Doubling

Journal of Climate ◽

10.1175/jcli-d-16-0293.1 ◽

2016 ◽

Vol 29 (18) ◽

pp. 6765-6782 ◽

Cited By ~ 12

Author(s):

Hansi K. A. Singh ◽

Cecilia M. Bitz ◽

Aaron Donohoe ◽

Jesse Nusbaumer ◽

David C. Noone

Keyword(s):

Moisture Transport ◽

Large Scale ◽

Climate Model ◽

Hydrological Cycle ◽

Global Climate ◽

Global Climate Model ◽

Mathematical Framework ◽

Surface Evaporation ◽

And Shifts

Abstract The aerial hydrological cycle response to CO2 doubling from a Lagrangian, rather than Eulerian, perspective is evaluated using information from numerical water tracers implemented in a global climate model. While increased surface evaporation (both local and remote) increases precipitation globally, changes in transport are necessary to create a spatial pattern where precipitation decreases in the subtropics and increases substantially at the equator. Overall, changes in the convergence of remotely evaporated moisture are more important to the overall precipitation change than changes in the amount of locally evaporated moisture that precipitates in situ. It is found that CO2 doubling increases the fraction of locally evaporated moisture that is exported, enhances moisture exchange between ocean basins, and shifts moisture convergence within a given basin toward greater distances between moisture source (evaporation) and sink (precipitation) regions. These changes can be understood in terms of the increased residence time of water in the atmosphere with CO2 doubling, which corresponds to an increase in the advective length scale of moisture transport. As a result, the distance between where moisture evaporates and where it precipitates increases. Analyses of several heuristic models further support this finding.

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On the parallelisation of weather and climate models

MAUSAM ◽

10.54302/mausam.v52i1.1687 ◽

2021 ◽

Vol 52 (1) ◽

pp. 191-200

Author(s):

S. K. DASH

Keyword(s):

Climate Models ◽

Climate Model ◽

Weather Forecasting ◽

Numerical Models ◽

Global Climate ◽

Global Climate Model ◽

Maximum Efficiency ◽

Computing Power ◽

Weather And Climate ◽

The Status

The numerical models used for weather forecasting and climate studies need very large computing resources. The current research in the field indicates that for accurate forecasts, one needs to use models at very high resolution, sophisticated data assimilation techniques and physical parameterisation schemes and multi-model ensemble integrations. In fact the spatial resolution required for accurate forecasts may demand computing power which is prohibitively high considering the processing power of a single processor of any supercomputer. During the last two decades, the developments in computing technology show the emergence of parallel computers with a number of processors which are capable of supplying enormously large computing power as against a single computer. Today, a cluster of workstations or personal computers can be used in parallel to integrate a global climate model for a long time. However, there are bottlenecks to be overcome in order to achieve maximum efficiency. Inter-processor communication is the key issue in case of global weather and climate models. The present paper aims at discussing the status of parallelisation of weather and climate models at leading centres of operational forecasting and research, the inherent parallelism in weather and climate models, the problems encountered in inter-processing communication and various ways of achieving maximum parallel efficiency.

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Additional global climate cooling by clouds due to ice crystal complexity

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-15767-2018 ◽

2018 ◽

Vol 18 (21) ◽

pp. 15767-15781 ◽

Cited By ~ 9

Author(s):

Emma Järvinen ◽

Olivier Jourdan ◽

David Neubauer ◽

Bin Yao ◽

Chao Liu ◽

...

Keyword(s):

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Short Wave ◽

Ice Crystals ◽

Asymmetry Factor ◽

Ice Crystal ◽

Data Set ◽

Angular Scattering

Abstract. Ice crystal submicron structures have a large impact on the optical properties of cirrus clouds and consequently on their radiative effect. Although there is growing evidence that atmospheric ice crystals are rarely pristine, direct in situ observations of the degree of ice crystal complexity are largely missing. Here we show a comprehensive in situ data set of ice crystal complexity coupled with measurements of the cloud angular scattering functions collected during a number of observational airborne campaigns at diverse geographical locations. Our results demonstrate that an overwhelming fraction (between 61 % and 81 %) of atmospheric ice crystals sampled in the different regions contain mesoscopic deformations and, as a consequence, a similar flat and featureless angular scattering function is observed. A comparison between the measurements and a database of optical particle properties showed that severely roughened hexagonal aggregates optimally represent the measurements in the observed angular range. Based on this optical model, a new parameterization of the cloud bulk asymmetry factor was introduced and its effects were tested in a global climate model. The modelling results suggest that, due to ice crystal complexity, ice-containing clouds can induce an additional short-wave cooling effect of −1.12 W m2 on the top-of-the-atmosphere radiative budget that has not yet been considered.

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Additional Global Climate Cooling by Clouds due to Ice Crystal Complexity

10.5194/acp-2018-491 ◽

2018 ◽

Author(s):

Emma Järvinen ◽

Olivier Jourdan ◽

David Neubauer ◽

Bin Yao ◽

Chao Liu ◽

...

Keyword(s):

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Ice Crystals ◽

Asymmetry Factor ◽

Ice Crystal ◽

Ice Clouds ◽

Submicron Structures ◽

Climate Cooling

Abstract. Ice crystal submicron structures have a large impact on the optical properties of cirrus clouds and consequently on their radiative effect. Although there is growing evidence that atmospheric ice crystals are rarely pristine, direct in-situ observations of the degree of ice crystal complexity are largely missing. Here we show a comprehensive in-situ dataset of ice crystal complexity coupled with measurements of the cloud asymmetry factor collected at diverse geographical locations. Our results demonstrate that an overwhelming fraction (between 61 and 81 %) of atmospheric ice crystals in the different regions sampled contain submicron deformations and, as a consequence, a low asymmetry factor of 0.75 is observed. The measured cloud angular light scattering functions were parameterized in terms of the cloud bulk asymmetry factor and tested in a global climate model. The modelling results suggest that due to ice crystal complexity, ice clouds can induce an additional cooling effect of −1.12 W m−2 on the radiative budget that has not yet been considered.

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Cirrus Cloud Microphysical Properties and Aerosol Indirect Effects using Airborne Observations and a Global Climate Model

10.31979/etd.t5pv-7w26 ◽

2020 ◽

Author(s):

Ryan Patnaude

Keyword(s):

Indirect Effects ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Cirrus Cloud ◽

Aerosol Indirect Effects ◽

Microphysical Properties

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Global-scale Aircraft Observations and Simulations of Cirrus Clouds and Aerosol Indirect Effects

10.5194/egusphere-egu21-420 ◽

2021 ◽

Author(s):

Minghui Diao ◽

Ryan Patnaude ◽

Xiaohong Liu ◽

Suqian Chu

Keyword(s):

Indirect Effects ◽

Climate Model ◽

Global Climate Model ◽

Cirrus Clouds ◽

Key Factors ◽

Aerosol Indirect Effects ◽

Dynamic Conditions ◽

In Situ Observations ◽

The U.S

Cirrus clouds have widespread coverage over Earth's surface area. Cirrus cloud radiative forcings are directly affected by the microphysical properties of cirrus clouds, including ice water content (IWC), ice crystal number concentration (Nice), and mean diameter (Dice). In this work, in-situ observations obtained from seven flight campaigns funded by the U.S. National Science Foundation are used to examine key factors controlling the formation and evolution of cirrus clouds. These key factors include thermodynamic conditions (i.e., temperature and relative humidity), dynamic conditions (i.e., vertical velocity), and aerosol indirect effects from larger and smaller aerosols (> 500 nm and > 100 nm, respectively). After isolating the effects from thermodynamic and dynamic conditions, we found that when aerosol number concentrations (Na500 and Na100) increase, IWC, Nice and Dice all increase. In particular, IWC and Nice increase significantly when Na is about 3 &#8211; 10 times larger than the average Na conditions (Patnaude and Diao, GRL, 2020).Simulations of cirrus clouds by a global climate model &#8211; the U.S. National Center for Atmospheric Research (NCAR) Community Atmosphere Model version 6 (CAM6) are evaluated against in-situ observations (Patnaude, Diao, Liu and Chu, ACP, accepted). Observations show higher Nice in the northern hemisphere (NH) midlatitude than southern hemisphere (SH) midlatitude. CAM6 simulations show &#8220;too many&#8221; and &#8220;too small&#8221; ice crystals in most of the regions except NH midlatitude, where simulations show lower Nice than the observations. Weaker aerosol indirect effects on cirrus clouds are also seen in the simulations compared with observations.

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