Bryan N. Lawrence

Cloud retrievals from satellite data using optimal estimation: evaluation and application to ATSR

Clouds play an important role in balancing the Earth’s radiation budget. Hence, it is vital that cloud climatologies are produced that quantify cloud macro and micro physical parameters and the associated uncertainty. In this paper, we present an algorithm ORAC (Oxford-RAL retrieval of Aerosol and Cloud) which is based on fitting a physically consistent cloud model to satellite observations simultaneously from the visible to the mid-infrared, thereby ensuring that the resulting cloud properties provide both a good representation of the short-wave and long-wave radiative effects of the observed cloud. The advantages of the optimal estimation method are that it enables rigorous error propagation and the inclusion of all measurements and any a priori information and associated errors in a rigorous mathematical framework. The algorithm provides a measure of the consistency between retrieval representation of cloud and satellite radiances. The cloud parameters retrieved are the cloud top pressure, cloud optical depth, cloud effective radius, cloud fraction and cloud phase. The algorithm can be applied to most visible/infrared satellite instruments. In this paper, we demonstrate the applicability to the Along-Track Scanning Radiometers ATSR-2 and AATSR. Examples of applying the algorithm to ATSR-2 flight data are presented and the sensitivity of the retrievals assessed, in particular the algorithm is evaluated for a number of simulated single-layer and multi-layer conditions. The algorithm was found to perform well for single-layer cloud except when the cloud was very thin; i.e., less than 1 optical depths. For the multi-layer cloud, the algorithm was robust except when the upper ice cloud layer is less than five optical depths. In these cases the retrieved cloud top pressure and cloud effective radius become a weighted average of the 2 layers. The sum of optical depth of multi-layer cloud is retrieved well until the cloud becomes thick, greater than 50 optical depths, where the cloud begins to saturate. The cost proved a good indicator of multi-layer scenarios. Both the retrieval cost and the error need to be considered together in order to evaluate the quality of the retrieval. This algorithm in the configuration described here has been applied to both ATSR-2 and AATSR visible and infrared measurements in the context of the GRAPE (Global Retrieval and cloud Product Evaluation) project to produce a 14 yr consistent record for climate research.

Variability in the mesosphere observed by the Nimbus 6 pressure modulator radiometer

The pressure modulator radiometer flew aboard Nimbus 6, collecting radiance data from June 1975 until June 1978. These data have been processed to yield daily temperatures, geopotential heights, and balance wind estimates from the stratosphere and mesosphere (30–85 km) for the entire period. We use these data to examine the variability of both the zonal-mean and the nonzonal disturbances present in the data. In terms of the zonal-mean, we show that the COSPAR International Reference Atmosphere (1986), developed from these data, can be misleading in the mesosphere due to the underlying interannual variability and the merging with other data sets. Daily variability of the zonal-mean flow is examined, and these data show strong evidence of coupling between the stratosphere and mesosphere for such variations. We also find evidence for significant coupling of wave-like events in the stratosphere and the mesosphere but that not all such disturbances seen in the mesosphere are due to simple propagation from below. Space-time spectral analysis is used to search for traveling planetary waves: Results show a weak 5-day normal mode present in the Equinox seasons, which appears to correspond to the first symmetric mode predicted by theory. These data also show clear evidence of the 4-day wave in all three southern winters examined and are consistent with the hypothesis that this mode grows due to instability of the background zonal flow.

High-resolution global climate modelling: the UPSCALE project, a large-simulation campaign

The UPSCALE (UK on PRACE: weatherresolving Simulations of Climate for globAL Environmental risk) project constructed and ran an ensemble of HadGEM3 (Hadley Centre Global Environment Model 3) atmosphereonly global climate simulations over the period 1985–2011, at resolutions of N512 (25 km), N216 (60 km) and N96 (130 km) as used in current global weather forecasting, seasonal prediction and climate modelling respectively. Alongside these present climate simulations a parallel ensemble looking at extremes of future climate was run, using a timeslice methodology to consider conditions at the end of this century. These simulations were primarily performed using a 144 million core hour, single year grant of computing time from PRACE (the Partnership for Advanced Computing in Europe) in 2012, with additional resources supplied by the Natural Environment Research Council (NERC) and the Met Office. Almost 400 terabytes of simulation data were generated on the HERMIT supercomputer at the High Performance Computing Center Stuttgart (HLRS), and transferred to the JASMIN super-data cluster provided by the Science and Technology Facilities Council Centre for Data Archival (STFC CEDA) for analysis and storage. In this paper we describe the implementation of the project, present the technical challenges in terms of optimisation, data output, transfer and storage that such a project involves and include details of the model configuration and the composition of the UPSCALE data set. This data set is available for scientific analysis to allow assessment of the value of model resolution in both present and potential future climate conditions.

Gravity wave drag in three‐dimensional atmospheric models of Mars

Gravity waves are disturbances whose restoring force is buoyancy. In the atmosphere they are made possible by the variation of potential temperature with height. They can be excited by various mechanisms including flow over orography. The momentum carried by these disturbances can exert significant drag forces on the mean flow in the terrestrial mesosphere. One parameterization of this effect, the Lindzen gravity wave drag scheme, is inserted into two simplified general circulation models (GCMs) of the Martian atmosphere, and its effects are described. The influence of large-amplitude, planetary-scale topography on wave breaking altitudes is discussed. We show that above 60 km in altitude, gravity wave drag dominates the momentum balance of the Martian atmosphere on the largest scales. This indirectly alters the thermal state of the atmosphere through the thermal wind relation. Model winds at this level are consistent with other, simpler studies, as well as with Earth-based spectroscopic observations. Below 60 km, the effects of planetary wave-mean flow interaction, as well as heating associated with Hadley circulation descent, are significant in determining the wind strength. Eddy diffusion coefficients derived from the Lindzen parameterization above 50 km are consistent with values implied from chemical modeling of the Martian middle atmosphere, as well as with simpler models of gravity wave drag.

Dynamical Evolution of the Northern Stratosphere in Early Winter 1991/92, as Observed by the Improved Stratospheric and Mesospheric Sounder

Abstract Dynamical fields based on temperature measurements from the Improved Stratospheric and Mesospheric Sounder on the Upper Atmosphere Research Satellite are presented for the Northern Hemisphere stratosphere for the period 28 October 1991 through 18 January 1992. Interpretation of these fields gives a picture of the dynamical evolution of this period in terms of the zonal-mean fields and the synoptic structures. Among the features of interest are the movements of the zonal-mean jets and several periods of stratospheric warming, culminating in a near-major warming in January.

Storing and manipulating environmental big data with JASMIN

JASMIN is a super-data-cluster designed to provide a high-performance high-volume data analysis environment for the UK environmental science community. Thus far JASMIN has been used primarily by the atmospheric science and earth observation communities, both to support their direct scientific workflow, and the curation of data products in the STFC Centre for Environmental Data Archival (CEDA). Initial JASMIN configuration and first experiences are reported here. Useful improvements in scientific workflow are presented. It is clear from the explosive growth in stored data and use that there was a pent up demand for a suitable big-data analysis environment. This demand is not yet satisfied, in part because JASMIN does not yet have enough compute, the storage is fully allocated, and not all software needs are met. Plans to address these constraints are introduced.

Information in environmental data grids

Providing homogeneous access (‘services’) to heterogeneous environmental data distributed across heterogeneous computing systems on a wide area network requires a robust information paradigm that can mediate between differing storage and information formats. While there are a number of ISO standards that provide some guidance on how to do this, the information landscape within domains is not well described. In this paper, we present an information taxonomy and two information components, which have been built for a specific application. These two components, one to aid data understanding and the other to aid data manipulation, are both deployed in the UK NERC DataGrid as described elsewhere.

The 4-day wave in the Antarctic mesosphere

A zonal wave number one eastward propagating planetary wave observed in the high latitude winter stratosphere with a period near 4 days has been studied by a number of previous authors. Radar observations coupled with stratospheric analyses are here used to demonstrate that this wave, known as the 4-day wave, extends into the Antarctic upper mesosphere. Previous workers have asserted that the wave is a manifestation of the observation of warm pools rotating in the polar vortex, and that the pool seems to behave in a quasi-nondispersive manner. The observation of the 4-day wave in the upper mesosophere presented here appears to validate previous claims that the warm pools are being maintained by wavelike dynamics, rather than simple advection.

Annual variation of airglow heights derived from wind measurements

Three independent techniques for measuring wind in the mesosphere and lower thermosphere region were compared using simultaneous measurements during the period May 1997 to April 1998. The three instruments used, a Fabry-Perot spectrometer, a medium frequency radar, and a meteor radar, are located on New Zealands South Island. The results obtained during this investigation show reasonable agreement amongst the three methods, in particular between the Fabry-Perot and the meteor radar. Correlation analysis of the meteor radar height-resolved winds and the Fabry-Perot spectrometer winds provides a valuable method for determining airglow heights. The results from the height determinations show a yearly variation of the OH emission layer, with its lowest height during summer, while the OI emission layer is found to remain at a relatively constant height.

Measurements of N2O by the UARS Improved Stratospheric and Mesospheric Sounder during the Early Northern Winter 1991/92

Abstract Measurements of stratospheric nitrous oxide made by the Improved Stratospheric and Mesospheric Sounder (ISAMS) during the period 28 October 1991–18 January 1992 are presented. The data are consistent with the dynamical fields at the time, and are in extremely good qualitative agreement with similar data from the Nimbus-7 SAMS and the Upper Atmosphere Research Satellite (UARS) Cryogenic Limb Array Etalon Spectrometer (CLAES) instruments, although in some regions the values are higher than have been obtained elsewhere. A major problem in the retrieval of the data has been contamination of the measured signal by aerosol emitted during the Mount Pinatubo eruption of June 1991. Despite the uncertainty in the values, the ISAMS N2O measurements provide a unique opportunity to study the synoptic evolution of a long-lived chemical tracer throughout the early winter, with near-continuous high-resolution measurements. The zonally averaged data are shown, as well as the measurements in the Northern Hemispher...