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doi: 10.1002/qj.49710142902pmid: N/A
A numerical ‘parameterization’ model has been developed in order to predict precipitation amount over hilly terrain in North Wales. The model enables calculations to be made of the vertical velocity profile resulting from orographic and large‐scale baroclinic effects at grid points one kilometre apart over an area of 2400km2. In the present study the precipitation falling on an area of 103km2, and on areas of order 102km2 within the larger area has been predicted, using as the input to the model large‐scale wind and humidity values derived from radiosonde ascents. Seven case studies are presented. All are examples of fast moving baroclinic systems. This type of system was chosen to minimize the effects of non‐orographic mesoscale or convective mechanisms, which are not parameterized in the present model. The mean error in the predicted rainfall over 103km2 was ± 10% and over 102km2 about ± 20%.
Barnett, J. J.; Harwood, R. S.; Houghton, J. T.; Morgan, C. G.; Rodgers, C. D.; Williamson, E. J.
doi: 10.1002/qj.49710142903pmid: N/A
Comparisons have been made between satellite measured radiances and those derived from radiosonde/rocketsonde profiles for several samples for both the Nimbus 4 and Nimbus 5 selective chopper radiometers during the period 1970–1973. Agreement between satellite and radiosonde measurements in the upper troposphere and lower stratosphere is better than 1 K in equivalent temperature. For rocketsonde observations mean differences of up to 3 K in equivalent temperature are found but these are within the combined experimental error of the measurements. Good confidence can, therefore, be placed on the method based on laboratory measured transmissions of deriving weighting functions for the satellite instruments.
doi: 10.1002/qj.49710142904pmid: N/A
A diagnostic dynamical study is presented of the three‐dimensional field of motion based on data from dropsondes released through the warm‐frontal rainband situation of 18 January 1971, and is complementary to an earlier radar‐synoptic study of this situation.
doi: 10.1002/qj.49710142905pmid: N/A
The horizontal cross‐sectional shape of the temperature field of convective plumes at a height of 3·5m in the atmospheric surface layer was observed to be very elongated in the downwind direction with a ratio of downstream to cross‐stream diameters of about 8:1. A dynamic explanation for this elongated shape is presented, based upon the minimization of the heat flux lost by a plume due to turbulent mixing around its boundary.
doi: 10.1002/qj.49710142906pmid: N/A
It is found that the mean meridional distribution of temperature, cloud cover and meridional energy flux can be predicted with extraordinary accuracy by application of a simple minimum principle to a multi‐box model of the globe which contains no direct specification of the system dynamics. The minimized quantity is related to the global net rate of production of entropy. It is the sum over all latitude zones of the ratio of net radiant energy input to the effective emission temperature of the zone. The result suggests that global dynamics is something of a passive variable which alters so as to satisfy a condition akin to minimum energy dissipation.
doi: 10.1002/qj.49710142907pmid: N/A
During two flight series of superpressure constant‐level balloons conducted in the lower stratosphere by the Laboratoire de Météorologie Dynamique, the vertical wind shear vector over 100 metres has been measured. It has been found from a record of almost two months that the r.m.s. wind shear is about 1·5 × 10−2s−1. The shear can reach 5 × 10−2s−1 in association with a breakdown of the stably stratified flow. From the records of wind shear vectors over 100 metres, 15 wind shear hodographs have been drawn which in turn have been divided in two groups. In the first group, the shear vector keeps a constant direction with time and in the second one it rotates anticlockwise with a 7 to 8·5 hour period suggesting the existence of gravity‐inertia waves in the flow. The modulus of the wind shear oscillates with a similar period but this feature is found whichever the group to which the hodograph belongs.
doi: 10.1002/qj.49710142908pmid: N/A
We examine the baroclinic instability problem in some simple two‐level models on a sphere. We find that there are large momentum transports associated with the growing waves. These transports are induced by aspects of the spherical geometry other than those included in the beta‐plane analysis. On the other hand, the beta‐plane gives a good description of the essential dynamics of the waves.
doi: 10.1002/qj.49710142909pmid: N/A
Land‐ and sea‐breeze circulations are simulated in a mathematical model, using a stably stratified atmosphere as a basic state. The results show that the land‐breeze is weaker than the sea‐breeze even although the heat contrast at the coast is identical in both cases. This is consistent with estimates of the corresponding model energy available potential.
Caughey, S. J.; Readings, C. J.
doi: 10.1002/qj.49710142910pmid: N/A
The dependences of the standard deviations of temperature (σr), total horizontal and vertical velocities (σuH and σw respectively) on local parameters are investigated in the atmospheric boundary layer. Useful expressions are obtained that enable rough estimates of σw and σT to be made in the bulk of the boundary layer.
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