Representativity error for temperature and humidity using the Met Office high-resolution model

The observation-error covariance matrix used in data assimilation contains contributions from instrument errors, representativity errors and errors introduced by the approximated observation operator. Forward model errors arise when the observation operator does not correctly model the observations or when observations can resolve spatial scales that the model cannot. Previous work to estimate the observation-error covariance matrix for particular observing instruments has shown that it contains signifcant correlations. In particular, correlations for humidity data are more significant than those for temperature. However it is not known what proportion of these correlations can be attributed to the representativity errors. In this article we apply an existing method for calculating representativity error, previously applied to an idealised system, to NWP data. We calculate horizontal errors of representativity for temperature and humidity using data from the Met Office high-resolution UK variable resolution model. Our results show that errors of representativity are correlated and more significant for specific humidity than temperature. We also find that representativity error varies with height. This suggests that the assimilation scheme may be improved if these errors are explicitly included in a data assimilation scheme. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland

The earth's hydrological cycle

This book gives a comprehensive presentation of our present understanding of the Earth's Hydrological cycle and the problems, consequences and impacts that go with this topic. Water is a central component in the Earth's system. It is indispensable for life on Earth in its present form and influences virtually every aspect of our planet's life support system. On relatively short time scales, atmospheric water vapor interacts with the atmospheric circulation and is crucial in forming the Earth's climate zones. Water vapor is the most powerful of the greenhouse gases and serves to enhance the tropospheric temperature. The dominant part of available water on Earth resides in the oceans. Parts are locked up in the land ice on Greenland and Antarctica and a smaller part is estimated to exist as groundwater. If all the ice over the land and all the glaciers were to melt, the sea level would rise by some 80 m. In comparison, the total amount of water vapor in the atmosphere is small; it amounts to ~ 25 kg/m2, or the equivalent of 25 mm water for each column of air. Yet atmospheric water vapor is crucial for the Earth’s energy balance. The book gives an up to date presentation of the present knowledge. Previously published in Surveys in Geophysics, Volume 35, No. 3, 201

Balance, potential-vorticity inversion, Lighthill radiation, and the slow quasimanifold

Practically our entire understanding of large-scale atmosphere–ocean dynamics depends on the notions of balance and potential-vorticity inversion. These are essential, for instance, for a clear understanding of the basic Rossby-wave propagation mechanism, or quasi-elasticity, that underlies almost every large-scale fluid-dynamical phenomenon of meteorological and oceanographical interest, from the global-scale transport of terrestrial greenhouse gases (and similar problems in the solar interior) to Rossby-wave-mediated global teleconnection, baroclinic and barotropic shear instability, vortex coherence, and vortex-core isolation. The ideas involved in understanding balance and inversion continue to hold special fascination because of their central importance both for theory and for applications, such as data assimilation, and the fact that complete mathematical understanding is still elusive. The importance for applications was adumbrated by Richardson in his pioneering study of numerical weather prediction. The importance for theory — and the exquisite subtlety involved — was adumbrated by Poincaré in his discovery of the homoclinic tangle, and by Lighthill in his discovery of the quadrupole nature of acoustic radiation by unsteady vortical motio

The quasi-biennial oscillation (QBO) : some points about the terrestrial QBO and the possibility of related phenomena in the solar interior

As Professor Holton has reminded us (q.v., this Proceedings), the terrestrial quasibiennial oscillation or QBO is a remarkably persistent phenomenon. It has been clearly seen in tropical meteorological radiosonde data since the early 1950s, and there is indirec

Assimilation of Streamflow Observations

Streamflow is arguably the most important predictor in operational hydrologic forecasting and water resources management. Assimilation of streamflow observations into hydrologic models has received growing attention in recent decades as a cost-effective means to improve prediction accuracy. Whereas the methods used for streamflow data assimilation (DA) originated and were popularized in atmospheric and ocean sciences, the nature of streamflow DA is significantly different from that of atmospheric or oceanic DA. Compared to the atmospheric processes modeled in weather forecasting, the hydrologic processes for surface and groundwater flow operate over a much wider range of time scales. Also, most hydrologic systems are severely under-observed. The purpose of this chapter is to provide a review on streamflow measurements and associated uncertainty and to share the latest advances, experiences gained, and science issues and challenges in streamflow DA. Toward this end, we discuss the following aspects of streamflow observations and assimilation methods: (1) measurement methods and uncertainty of streamflow observations, (2) streamflow assimilation applications, and (3) benefits and challenges streamflow DA with regard to large-scale DA, multi-data assimilation, and dealing with timing errors