engleski

On some recent advances in mountain meteorology

As meteorological observational network is becoming increasingly more sophisticated on one side, and resolution in numerical weather (and even climate) prediction models deploys ever finer resolution on another side, Mountain Meteorology (MM) nowadays is clearly gaining progressively higher importance in science, applications and daily course of lives. This semicomprehensive overview of recent advances in MM, stretching from the late 1970’s onwards, touches upon several points. The following issues will be assessed at various depths: katabatic and anabatic flows, mountain waves, severe downslope windstorms (including bora wind) and forced deep convection (tackling some aspects of heavy orographic precipitation). The most comprehensive and useful reviews of mountain meteorology are those by Smith (1979, 1989). He goes beyond slope winds and buoyancy waves, toward various types of windstorms and orographic precipitation. Egger and Hoinka (1992) deal with terrain influences on large scale frontal passages ; these effects are different at various mountain regions. Doyle and Durran (2002) are among the first to quantitatively address meso- and micro-scale mountain lee-side processes due to the wave-induced rotors and low-level turbulence. Grisogono and Enger (2004) show, in an idealistic model setup, how and why terrain-induced atmospheric boundary-layer (ABL) effects are asymmetric with respect to the mountain orientation toward the incoming flow. Meanwhile, Večenaj et al. (2011) are among the first to quantitatively assess, based on observations, spatially inhomogeneous boundarylayer structure offshore in the lee of intensive coastal mountain-wave airflow. Grisogono and Belušić (2009) provide a most recent review of severe downslope windstorms (particularly focused on bora wind). For instance, subtle Coriolis effects on mountain-induced wave-breaking process are still poorly understood nowadays. The figure shows the low-level flow, i.e., the nearly horizontal wind field (U, V), over an idealized mesoscale mountain without (left) or with (right) a pass in the middle of the mountain. For a non-zero Coriolis parameter, lee-side eddy shedding and mountain wakes become asymmetric, as do the lowlevel jets (lower subplots). Therefore, the processes in the ABL over complex terrain can be greatly affected by mountain waves and wakes. These in turn, may influence cloud formation, air-pollution and transport of pollutants and deep convection. Relations toward further vigorous atmospheric research in Nepal, MM in particular, will be addressed. Forecasting deep convection in mountainous regions, pertaining to lightning and other atmosphere-related severe effects, will be tackled. However, some of these issues shall remain just barely touched upon, thus longing for further rapid research competing in time with the increasing needs due to alarming climate changes in the broader region of the Himalaya.

valley flows; mountain waves; downslope windstorms; orographic deep convection

Prof. dr. sc. Branko Grisogono sudjelovao je u svojstvu 'resource person' pozvanim predavanjem na Simpoziju kojeg su zajednički organizirali: Ministarstvo znanosti i tehnologije Vlade Nepala (MOST), Nepalska akademija znanosti i tehnologije (NAST) i Centar za znanost i tehnologiju Nesvrstanih i drugih zemalja u razvoju (NAM S&T Centre, New Delhi, India). Poziv je upućen od strane Organizacijskog odbora Simpozija. Više o Simpoziju na http://www.researchsea.com/html/calendar.php/eid/6367/cid/2/research/2nd_international_symposium_on_lightning_protection.html?PHPSESSID=hpkvjvttgoau1vtk9r1cq7s5g4