Figure 5 depicts, from d04, latitudinal cross sections red lines in Fig. UP1 and UP2 are the locations where the Froude number upstream the mountain is calculated. The tight isentropes on the windward side of the mountains to the right in Fig. The temperature profile in Fig. The latter height is therefore a critical level since the cross-mountain flow component becomes null; thus, triggered gravity waves will break and dissipate when they approach it.
Markowski and Richardson outline seven conditions conducive to DSWS, albeit not all of them absolutely necessary. These conditions are 1 an asymmetric mountain with steeper lee than windward side Fig. Apart from this, 6 reverse wind shear above Figs. These conditions are all perfectly met for both locations analyzed, as discussed previously, and indeed intense DSWSs occur in both cases. The gray zone represents nighttime. Wind barb profile for each pair of points at right.
The stably stratified cross-barrier flow displays wave activity from early on, and wave breaking, as the vertical isentropes suggest Fig. In both cases, isentropes on the windward side sink sharply under these layers of low stability on the lee side, much more pronouncedly for the tallest mountain Fig.
Encompassing the well-mixed region to the lee, a split streamline develops Smith , b and below its lower branch there is flow thinning and a significant increase in wind speed. However, the particular features existent on the lee side differ, depending of the height of the topographic obstacle. The strong accelerated flow confined by layers of strong wind shear and turbulence extends for many kilometers downwind from the lowest mountain Fig.
The formation of either of these lee wave events is related to the Froude number upstream Smith , We note that only the turbulence produced by the existent wind shear in the column is well captured in the simulation Fig. The subgrid-scale turbulence associated with gravity waves due to rotors and nonlocal turbulent advection or with instability resulting from wave overturning is not represented and accounted for since a much higher horizontal and vertical resolution on the order of tens of meters would be needed in order to explicitly resolve these features Vosper et al.
Figure 6 a plots the Froude number Eq. This is where the highest wind speeds are found. Stability is sharply reduced aloft, in the region encompassed by the dividing streamline, and winds are rather weak and have an easterly component for the most part, parallel to the mountains. Wave overturning and breaking is also much more pronounced Fig. A rotor extending from the jump to the location of observation station MET2 is also evident in Fig. The temperature profile upstream is very similar to that of the MET1 case, but downwind from the mountain at location MET2 lacks the strongly stratified layer present in the case of the lower mountain.
We note that the soundings in Fig. Results from the innermost nested grid d05 with the finest resolution Fig. Waves are absent further east in the MET2 cross section, where the topographic barrier is higher and a stationary HJ forms instead, as discussed above.
Figure 7 As in Fig. Our results suggest that during Tehuano wind events, the Pacific side of the Isthmus of Tehuantepec east of Chivela Pass is very prone to host extreme wind phenomena. The formation of DSWSs in the area increases the impacts of the already strong mountain gap winds. Finally, we contrast our simulation results with the very few data available for validation at meteorological stations MET1 and MET2.
The two plots in Fig. Figure 8 a Wind speed comparison among observations at MET1 green , and model output from d04 red , and d05 blue. Wind speed results from d04 and d05 at location MET1 are quite similar, and fare well with respect to observations Fig. The similarity in the low mean error between both simulations and their high correlation throughout the period are due to the nature of the event in that area, an intense and mostly steady jet that the d04 domain resolution 1.
The complexity and fast variability in HJ formation in this area are better resolved in the higher-resolution grid, which perhaps reproduces more accurately the stagnant flow and rotor formations downstream from the HJ. As in the case of wind speeds, wind direction results from the finer grid d05 are also better than in d Lee waves can promote orographic cloud formation at different scales, depending on the amplitude of the wave and elevation Armi and Mayr , ; Szmyd , Model results in d05 suggest that lenticular clouds form at the crests of the trapped lee waves depicted in Fig.
The actual existence of these lenticular clouds with the same location and pattern as in the simulation further validates the model results. In the present work, we studied lee wave phenomena occurring during Tehuano events on the Pacific side of the Isthmus of Tehuantepec using WRF high-resolution simulations. Orographic forcings at different scales result in the well-known gap wind jet off Chivela Pass, but also in downslope windstorms and hydraulic jumps in the neighboring mountains.
We analyzed these phenomena in an episode in December having the typical genesis of Tehuantepecer wind events. An Arctic air mass in North America pushed as far south as the Bay of Campeche due to cold air damming east of the Rockies continuing to the east of the Sierra Madre Oriental range in Mexico. The displacement of the associated high-pressure system on the wake of the cold front created large pressure differences across the Isthmus of Tehuantepec, ultimately producing the strong mountain gap winds through the low elevation of Chivela Pass.
The flow over these mountains results in intense DSWSs to their lee with the generation of intense turbulence, HJs and rotors, depending on the particular height of the topography.
The thermodynamic characteristics of the air masses are rather uniform upwind of both mountains, with strong stability within the cool pool and weaker above, and intense northerly winds that back and weaken aloft to a more easterly component parallel to the barrier. Wave breaking produces mixing and generates a region of low stability to the lee of the mountains, which is deeper where the waves have higher amplitude.
The Froude number is around 2. Wind speeds are reduced closer to the surface due to intense turbulence. The Froude number decreases to about 1 further east as elevation rises and the flow presents a critical regime. Isentropes on the windward side of the mountain sink much more pronouncedly under the wider mixed layer generated by wave breaking to the lee, and are tightly packed in a shallow layer above the surface.
Valle, On coastal currents of Tehuantepec. Distribution and abundance of tuna related to wind and ocean conditions in the Gulf of Tehuantepec, Mexico. FAO Fish. Rosales Hoz, E. Investigations of phosphorite deposits in the Gulf of Tehuantepec, Mexico. Morales de la Garza and L. Rosales Hoz, Tectonics, sedimentology and geochemistry. Inertial wind path and sea surface temperature patterns near the Gulf of Tehuantepec, Mexico and Gulf of Papagayo.
Freilich and S. Esbensen, Satellite observations of the wind jets off the Pacific coast of Central America. Weather Rev. Fischer, Barberan Falcon, Modificaciones al sistema de clasificacion climatica de Koppen. Talleres Larios, S. Deep Sea Res. Northers of the Gulf of Tehuantepec. Robles Jarero, M. Bazan Guzman and E. Phytoplankton productivity. A survey of worldwide sea surface temperature fronts detected by environmental satellites. Robles, M. Argote, E. Barton, R. Smith, J. Brown, M. Kosro, A.
Velez and J. Lee and D. Enfield, The response of the coastal ocean to strong offshore winds: with application to circulation in the Gulf of Tehuantepec and Papagayo.
Robinson, D. Ballestero and E. Posada dos Hermanas, a property with a garden, is located in Barra de la Cruz, 1. The nearest airport is Huatulco International Airport, 31 km from the bed and breakfast. This beachfront property offers access to a patio, darts, free private parking and free WiFi. This holiday home is fitted with 1 bedroom, a kitchen with fridge, a flat-screen TV, a seating area and 1 bathroom with a shower.
Towels and bed linen are featured in the holiday home. If you would like to discover the area, hiking, snorkelling and cycling are possible in the surroundings. The nearest airport is Huatulco International Airport, 22 km from the holiday home.
Set in Santa Cruz Huatulco, 1. The population is composed almost wholly of indigenous Zapotec peoples. The women are the traders and do little menial work. Known as "Tehuanas," these women are known throughout Mexico for their colorful dresses, assertive personalities, and relatively equal relations with men, leading some to characterize them as "matriarchal".
The predominant climates in the region are tropical savanna primarily in the south and tropical monsoon primarily in the north. There are also small central areas with a temperate climate due to elevation. The narrowness of the isthmus, and the gap in the Sierra Madre, allow the trade winds from the Gulf of Mexico to blow through to the Pacific.
Normally, these winds are not particularly strong.
0コメント