The summertime thermal circulation in the region of an asymmetric valley exit is investigated by means of observations and high-resolution model simulations. The northeastward-oriented Alpine Lech Valley opening into the Bavarian Alpine foreland has an eastern slope exceeding the western slope by about 15 km. Northerly winds along the eastern slope are frequently observed, reaching substantial strength during fair weather conditions. A field experiment has been conducted to explore this phenomenon and to pinpoint the connection of the northeasterly flow to the Lech Valley wind circulation. Numerical simulations have also been carried out to support the interpretation of the observations. It is found that the northerlies owe their existence to the dominantly easterly flow along the foothills of the Alps, which is partly induced by the Alpine heat low but may be strengthened by favorable synoptic conditions. Examples for both situations will be discussed. The diurnal flow in the Lech Valley has little obvious impact on these northeasterlies. On days with moderate synoptic easterly flow, a wake is present on the lee of the eastern slope of the exit region, accompanied by a shear zone along the edge of the wake. This shear zone is forced southward during the daytime because of thermally initiated pressure gradients between the Alpine foreland and the Alps, leading to sudden wind changes in the exit area at the time of its passage.

Experiment E865 at the BNL AGS is a search for the Lepton Family Violating decay K+→π+μ+e−1. We aim to reach a single event sensitivity below 10−11 for this decay. The E865 apparatus allow us to collect and study other rare and semi rare K+ decays. Preliminary results are shown on K+→π+μ+e−, K+→π+e+e−, K+→π+μ+μ−, K+→π+π−e+ν, K+→e+νe+e−, K+→μ+νe+e−, K+→π0e+ν (π0→e+e−γ).

The passage of a frontal zone over a two-dimensional triangular ridge is investigated using a semigeostrophic model. The model atmosphere consists of three layers of uniform density and potential vorticity. The densest (coldest) layer represents the airmass behind the cold front, the next layer the frontal zone itself, and the least dense (warmest) layer represents the flow ahead of and above the frontal zone. At ground level, the frontal zone is contained between two surface fronts. A prescribed pressure field imposes translation at a speed U, and confluence with a deformation rate alpha. A one-layer version of the model has also been considered. The main conclusions are that (a) the mountain-induced shift of the position of a front does not depend on U or alpha, it is mainly negative on the windward slope and the upper part of the leeward slope, but is positive in the downstream plain and on the lower part of the leeward slope (there are no effects far-afield), and (b) frontal collapse must occur for alpha > 0. The collapse is delayed over most of the mountain, compared to the no-mountain case, but occurs earlier downstream from the mountain. Prior to the collapse, there is up-slope frontogenesis when part of the frontal zone is in the plain. Frontolysis prevails if all of the frontal zone is on the up-slope and if a is not too large. Frontogenesis occurs on the down-slope and in the plain.

Employing the decay chain K+ --> pi+pi0, pi0 --> e+e- we have observed the decay pi0 --> e+e-. With a signal sample of almost-equal-to 21 events we measure the branching ratio for pi0 --> e+e- to be (6.9 +/-2.3 +/- 0.6) x 10(-8), normalized to the decay K+ --> pi+pi0, pi0 --> e+e-gamma. This result is consistent with the unitarity lower bound and the published 90% confidence level upper limit of 13 x 10(-8).

A shallow inversion layer with southeasterly outflow and a cyclonic vortex in the troposphere are the basic characteristics of the Antarctic mean circulation, An attempt is made to model this pattern in a two-layer representation of the atmosphere where all equations are averaged horizontally over the Antarctic domain. Cooling at the slope drives a direct circulation that acts as a source of westerly angular momentum. This momentum is transferred out of Antarctica by topographically modified large-scale waves, enforced at the northern boundary of the model. Two types of steady states are found for fixed frequency and zonal wavenumber: one where the wave is quite effective in performing the required momentum transport so that a qualitatively realistic circulation results and another one with strong upper-level westerlies but virtually no surface easterlies. A model climatology can be derived if stochastic forcing is added to the equations. It turns out that the distribution of the flow states is centered near a "realistic" equilibrium if a wave spectrum is prescribed at the northern boundary according to observations.

We present results of an experiment in which approximately 500 events of the decay K + --> pi+ e+ e-were observed. We have measured the branching ratio for K(pi-ee)+ to be (2.75 +/- 0.23 +/- 0.13) x 10(-7) assuming a vector interaction with a form factor of lambda = 0.105 +/- 0.035 +/- 0.015. We have also found the branching ratio times decay probability for K + --> pi+ X0, X0 --> e+ e- to be less than 1.5 x 10(-8) (99% C. L.) over an X0 invariant mass range from 150 to 340 MeV/c2.

A low-order model of global barotropic flow with intrinsic long-term variability is presented. The model is based on the barotropic vorticity equation with Newtonian forcing of the zonal flow and realistic orography. Subgrid eddy motion is represented by point vortices which move within the low-order flow of the model and affect it through their own circulation. The vortices are inserted at locations of maximum flow speed and are removed after a prescribed lifetime has elapsed. In the absence of Newtonian forcing, mid-latitude westerlies and strong polar easterlies are induced if there are only cyclonic vortices. Anticyclonic vortices create equatorial easterlies.If 'realistic' Newtonian forcing is added, two stationary orographic troughs dominate the model's mean flow in the northern hemisphere. Cyclones are generated downstream of the troughs, and pronounced storm tracks extend eastward from these genesis areas. The model atmosphere exhibits slow variability of a realistic order of magnitude with maxima over the 'oceans'. This long-term variability is due to the interaction of long-lived circulation patterns, like blocks, with the point vortices. Moreover, cyclone generation is important in inducing slow motions. In the southern hemisphere there is little variation of flow statistics with longitude. All in all the low-order model is surprisingly successful in simulating the observed patterns of atmospheric transience. This suggests that a low-order model with point vortices might be a useful tool in climate research.

E777 at the Brookhaven AGS has published a final branching ratio limit for the lepton family violating decay K{sup +} {yields} {pi}{sup +}{mu}{sup +}e{sup {minus}} of 2.1 {times} 10{sup {minus}10} (90% C.L.). New results based on approximately 500 events of the G.I. M. suppressed decay K{sup +} {yields} {pi}{sup +}e{sup +}e{sup {minus}} have yielded a branching ratio of (2.75 {plus minus} 0.23 {plus minus} 0.13) {times} 10{sup {minus}7} assuming a vector interaction with, a form factor = 0.105 {plus minus} 0.035 {plus minus} 0.015. The branching ratio times decay probability for K{sup 0} {yields} {pi}{sup +} X{sup 0}, ,{sup 0} {yields} e{sup +}e{sup {minus}} was found to less than 1.5 {times} 10{sup {minus}8} (99% C.L.) in the e{sup +}e{sup {minus}} invariant mass range of 150 to 340 MeV/c. An approved second generation experiment sensitive to K{sup +} {yields} {mu}{sup +}e{sup {minus}} at the 10{sup {minus}12} level is discussed. 5 refs., 3 figs.

The progress of AGS Experiment 777, a search for K+→π+μ+e− is described. Results on the decay K+→π+A0, where A0 is a weakly interacting neutral particle that decays into e+e− and preliminary results on the direct decay K+→π+e+e− are presented as well as new limits on π0→μ+e−.

A search for the lepton-flavor violating decay K/sup +/..--> pi../sup +/..mu../sup +/e/sup -/ has been performed. Measurements have also been made of the branching ratio and decay particle distributions for the decay K/sup +/..--> pi../sup +/e/sup -/. A description of the measurement technique, and preliminary results are presented. 6 refs., 5 figs.

The progress of AGS Experiment 777, a search for K/sup +/ ..-->.. ..pi../sup +/..mu../sup +/e/sup -/ is described. Results on the decay K/sup +/ ..-->.. ..pi../sup +/A/sup 0/, where A/sup 0/ is a weakly interacting neutral particle that decays into e/sup +/e/sup -/ and preliminary results on the direct decay K/sup +/ ..-->.. ..pi../sup +/e/sup +/e/sup -/ are presented as well as new limits on ..pi../sup 0/ ..-->.. ..mu../sup +/e/sup -/. 12 refs., 5 figs.

A search for the lepton-flavor violating decay K/sup +/..--> pi../sup +/..mu../sup +/e/sup -/ has been performed. Measurements have also been made of the branching ratio and decay particle distributions for the decay K/sup +/..--> pi../sup +/e/sup -/. A description of the measurement technique, and preliminary results are presented. 6 refs., 5 figs.

We report here on a search for the lepton-family-number-violating decay ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\mu}}^{+}{e}^{\ensuremath{-}}$. We found no evidence for this decay mode and we establish an upper limit on its branching ratio of 1.1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}9}$ at the 90% confidence level (C.L.) for a uniform phase-space decay distribution. We also use this result to establish an upper limit for the branching ratio of the decay ${\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{e}^{\ensuremath{-}}$ of 7.8\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ (90% C.L.).