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This article delivers a short history of the early quantitative documentation of a rotor-type circulation in the bora-type flow on the northern Adriatic by Andrija Mohorovičić, an all-around geophysicist and the father of Croatian geophysical research who is widely known as the discoverer of discontinuity between the Earth's crust and mantle. This historical work presents an overview of Mohorovičić's research technique and rotor-related contributions, together with a short account of other observations of rotors contemporary to Mohorovičić as well as those from the 1920s and 1930s, considered to be seminal work on the subject on atmospheric rotors to date. In the year that marks the 150th anniversary of Mohorovičićs birth, his early meteorological observations remain germane for atmospheric rotor research, which is currently experiencing a renaissance with the Terrain-Induced Rotor Experiment (T-REX), a recently completed international field campaign and an ongoing research effort focused on atmospheric terrain-induced rotors.
This article delivers a short history of the early quantitative documentation of a rotor-type circulation in the bora-type flow on the northern Adriatic by Andrija Mohorovičić, an all-around geophysicist and the father of Croatian geophysical research who is widely known as the discoverer of discontinuity between the Earth's crust and mantle. This historical work presents an overview of Mohorovičić's research technique and rotor-related contributions, together with a short account of other observations of rotors contemporary to Mohorovičić as well as those from the 1920s and 1930s, considered to be seminal work on the subject on atmospheric rotors to date. In the year that marks the 150th anniversary of Mohorovičićs birth, his early meteorological observations remain germane for atmospheric rotor research, which is currently experiencing a renaissance with the Terrain-Induced Rotor Experiment (T-REX), a recently completed international field campaign and an ongoing research effort focused on atmospheric terrain-induced rotors.
SIERRA WAVE PROJECT REVISITED
50 Years Later
The Sierra Wave Project was the first post–World War II (WWII) mountain meteorology field experiment in the United States designed to study mountain lee-wave phenomena. In its concept, design, organization, and execution, this Air Force–funded project served as an important predecessor of modern mesoscale field experiments proving clearly that mesoscale phenomena could be studied effectively by combining high-density ground-based and airborne observations. In this historical overview of the Sierra Wave Project, we set the scientific motivations for the experiment in their historical context, examine the coupling of the Air Force interests with the sport of soaring and the science of meteorology in this experiment, and evaluate the impact of the observational and theoretical programs of the Sierra Wave Project on the meteorological and aviation communities. We also provide a link to the related past investigations of mountain waves and an outlook for the future ones.
The Sierra Wave Project was the first post–World War II (WWII) mountain meteorology field experiment in the United States designed to study mountain lee-wave phenomena. In its concept, design, organization, and execution, this Air Force–funded project served as an important predecessor of modern mesoscale field experiments proving clearly that mesoscale phenomena could be studied effectively by combining high-density ground-based and airborne observations. In this historical overview of the Sierra Wave Project, we set the scientific motivations for the experiment in their historical context, examine the coupling of the Air Force interests with the sport of soaring and the science of meteorology in this experiment, and evaluate the impact of the observational and theoretical programs of the Sierra Wave Project on the meteorological and aviation communities. We also provide a link to the related past investigations of mountain waves and an outlook for the future ones.
Abstract
Recommendations are presented for in situ and remote sensing instruments and capabilities needed to advance the study of convection and turbulence in the atmosphere. These recommendations emerged from a community workshop held on 22–24 May 2017 at the National Center for Atmospheric Research and sponsored by the National Science Foundation. Four areas of research were distinguished at this workshop: i) boundary layer flows, including convective and stable boundary layers over heterogeneous land use and terrain conditions; ii) dynamics and thermodynamics of convection, including deep and shallow convection and continental and maritime convection; iii) turbulence above the boundary layer in clouds and in clear air, terrain driven and elsewhere; and iv) cloud microphysical and chemical processes in convection, including cloud electricity and lightning.
The recommendations presented herein address a series of facilities and capabilities, ranging from existing ones that continue to fulfill science needs and thus should be retained and/or incrementally improved, to urgently needed new facilities, to desired capabilities for which no adequate solutions are as yet on the horizon. A common thread among all recommendations is the need for more highly resolved sampling, both in space and in time. Significant progress is anticipated, especially through the improved availability of airborne and ground-based remote sensors to the National Science Foundation (NSF)-supported community.
Abstract
Recommendations are presented for in situ and remote sensing instruments and capabilities needed to advance the study of convection and turbulence in the atmosphere. These recommendations emerged from a community workshop held on 22–24 May 2017 at the National Center for Atmospheric Research and sponsored by the National Science Foundation. Four areas of research were distinguished at this workshop: i) boundary layer flows, including convective and stable boundary layers over heterogeneous land use and terrain conditions; ii) dynamics and thermodynamics of convection, including deep and shallow convection and continental and maritime convection; iii) turbulence above the boundary layer in clouds and in clear air, terrain driven and elsewhere; and iv) cloud microphysical and chemical processes in convection, including cloud electricity and lightning.
The recommendations presented herein address a series of facilities and capabilities, ranging from existing ones that continue to fulfill science needs and thus should be retained and/or incrementally improved, to urgently needed new facilities, to desired capabilities for which no adequate solutions are as yet on the horizon. A common thread among all recommendations is the need for more highly resolved sampling, both in space and in time. Significant progress is anticipated, especially through the improved availability of airborne and ground-based remote sensors to the National Science Foundation (NSF)-supported community.
THE TERRAIN-INDUCED ROTOR EXPERIMENT
A Field Campaign Overview Including Observational Highlights
The Terrain-Induced Rotor Experiment (T-REX) is a coordinated international project, composed of an observational field campaign and a research program, focused on the investigation of atmospheric rotors and closely related phenomena in complex terrain. The T-REX field campaign took place during March and April 2006 in the lee of the southern Sierra Nevada in eastern California. Atmospheric rotors have been traditionally defined as quasi-two-dimensional atmospheric vortices that form parallel to and downwind of a mountain ridge under conditions conducive to the generation of large-amplitude mountain waves. Intermittency, high levels of turbulence, and complex small-scale internal structure characterize rotors, which are known hazards to general aviation. The objective of the T-REX field campaign was to provide an unprecedented comprehensive set of in situ and remotely sensed meteorological observations from the ground to UTLS altitudes for the documentation of the spatiotemporal characteristics and internal structure of a tightly coupled system consisting of an atmospheric rotor, terrain-induced internal gravity waves, and a complex terrain boundary layer. In addition, T-REX had several ancillary objectives including the studies of UTLS chemical distribution in the presence of mountain waves and complex-terrain boundary layer in the absence of waves and rotors. This overview provides a background of the project including the information on its science objectives, experimental design, and observational systems, along with highlights of key observations obtained during the field campaign.
The Terrain-Induced Rotor Experiment (T-REX) is a coordinated international project, composed of an observational field campaign and a research program, focused on the investigation of atmospheric rotors and closely related phenomena in complex terrain. The T-REX field campaign took place during March and April 2006 in the lee of the southern Sierra Nevada in eastern California. Atmospheric rotors have been traditionally defined as quasi-two-dimensional atmospheric vortices that form parallel to and downwind of a mountain ridge under conditions conducive to the generation of large-amplitude mountain waves. Intermittency, high levels of turbulence, and complex small-scale internal structure characterize rotors, which are known hazards to general aviation. The objective of the T-REX field campaign was to provide an unprecedented comprehensive set of in situ and remotely sensed meteorological observations from the ground to UTLS altitudes for the documentation of the spatiotemporal characteristics and internal structure of a tightly coupled system consisting of an atmospheric rotor, terrain-induced internal gravity waves, and a complex terrain boundary layer. In addition, T-REX had several ancillary objectives including the studies of UTLS chemical distribution in the presence of mountain waves and complex-terrain boundary layer in the absence of waves and rotors. This overview provides a background of the project including the information on its science objectives, experimental design, and observational systems, along with highlights of key observations obtained during the field campaign.
Abstract
In this essay, we highlight some challenges the atmospheric community is facing concerning adequate treatment of flows over mountains and their implications for numerical weather prediction (NWP), climate simulations, and impact modeling. With recent increases in computing power (and hence model resolution) numerical models start to face new limitations (such as numerical instability over steep terrain). At the same time there is a growing need for sufficiently reliable NWP model output to drive various impact models (for hydrology, air pollution, agriculture, etc.). The input information for these impact models is largely produced by the boundary layer (BL) parameterizations of NWP models. All known BL parameterizations assume flat and horizontally homogeneous surface conditions, and their performance and interaction with resolved flows is massively understudied over mountains—hence their output may be accidentally acceptable at best. We therefore advocate the systematic investigation of the so-called “mountain boundary layer” (MoBL), introduced to emphasize its many differences to the BL over flat and horizontally homogeneous terrain.
An international consortium of scientists has launched a research program, TEAMx (Multi-Scale Transport and Exchange Processes in the Atmosphere over Mountains–Program and Experiment), to address some of the most pressing scientific challenges. TEAMx is endorsed by World Weather Research Programme (WWRP) and the Global Energy and Water Exchanges (GEWEX) project as a “cross-cutting project.” A program coordination office was established at the University of Innsbruck (Austria). This essay introduces the background to and content of a recently published white paper outlining the key research questions of TEAMx.
Abstract
In this essay, we highlight some challenges the atmospheric community is facing concerning adequate treatment of flows over mountains and their implications for numerical weather prediction (NWP), climate simulations, and impact modeling. With recent increases in computing power (and hence model resolution) numerical models start to face new limitations (such as numerical instability over steep terrain). At the same time there is a growing need for sufficiently reliable NWP model output to drive various impact models (for hydrology, air pollution, agriculture, etc.). The input information for these impact models is largely produced by the boundary layer (BL) parameterizations of NWP models. All known BL parameterizations assume flat and horizontally homogeneous surface conditions, and their performance and interaction with resolved flows is massively understudied over mountains—hence their output may be accidentally acceptable at best. We therefore advocate the systematic investigation of the so-called “mountain boundary layer” (MoBL), introduced to emphasize its many differences to the BL over flat and horizontally homogeneous terrain.
An international consortium of scientists has launched a research program, TEAMx (Multi-Scale Transport and Exchange Processes in the Atmosphere over Mountains–Program and Experiment), to address some of the most pressing scientific challenges. TEAMx is endorsed by World Weather Research Programme (WWRP) and the Global Energy and Water Exchanges (GEWEX) project as a “cross-cutting project.” A program coordination office was established at the University of Innsbruck (Austria). This essay introduces the background to and content of a recently published white paper outlining the key research questions of TEAMx.
