9 research outputs found
An observational study of a shallow gravity current triggered by katabatic flow
International audienceObservations from a wind profiler and a meteorological tower are utilized to study the evolution of a gravity current that passed over the Meteorological Research Institute's (MRI) field site in Tsukuba, Japan. The gravity current was created by katabatic flow originating on the mountainous slopes west of the field site. The passage of the shallow current was marked by a pronounced pressure disturbance and was accompanied by vertical circulations seen in the tower and profiler data. Direct vertical-beam measurements are difficult, especially at low heights during high-gradient events like density currents. In this study vertical velocities from the profiler are derived from the four oblique beams by use of the Minimizing the Variance of the Differences (MVD) method. The vertical velocities derived from the MVD method agree well with in situ vertical velocities measured by a sonic anemometer on the tower. The gravity current is analyzed with surface observations, the wind profiler/RASS and tower-mounted instruments. Observations from the profiler/RASS and the tower-mounted instruments illustrate the structure of the gravity current in both wind and temperature fields. The profiler data reveal that there were three regions of waves in the vertical velocity field: lee-type waves, a solitary wave and Kelvin-Helmholtz waves. The lee-type waves in the head region of the gravity current seem to have been generated by the gravity current acting as an obstacle to prefrontal flow. The solitary wave was formed from the elevated head of the gravity current that separated from the feeder flow. Profiler vertical-motion observations resolve this wave and enable us to classify it as a Benjamin-Davis-Ono (BDO) type solitary wave. The ducting mechanism that enabled the solitary wave to propagate is also revealed from the wind profiler/RASS measurements. The combination of high-resolution instruments at the MRI site allow us to develop a uniquely detailed picture of a shallow gravity current structure
Central-Pacific surface meteorology from the 2016 El Niño Rapid Response (ENRR) field campaign
During the early months of the 2015/2016
El Niño event, scientists led by the Earth System Research Laboratory's
Physical Sciences Division conducted the National Oceanic and Atmospheric
Administration's (NOAA's) El Niño Rapid Response (ENRR) field campaign.
One component of ENRR involved in situ observations collected over the
near-equatorial eastern–central Pacific Ocean. From 25 January to
28 March 2016, standard surface meteorology observations, including rainfall,
were collected at Kiritimati Island (2.0° N, 157.4° E) in
support of twice-daily radiosonde launches. From 16 February to
16 March 2016, continuous measurements of surface meteorology, sea surface
temperature, and downwelling shortwave radiation were made by NOAA Ship
Ronald H. Brown. These were largely done in support of the four to
eight radiosondes launched each day as the ship travelled from Hawaii to TAO
buoy locations along longitudes 140 and 125° W and then back to port
in San Diego, California. The rapid nature of these remote field deployments
led to some specific challenges in addition to those common to many surface
data collection efforts. This paper documents the two deployments as well as
the steps taken to evaluate and process the data. The results are two
multi-week surface meteorology data products and one accompanying set of
surface fluxes, all collected in the core of the eastern–central Pacific's
extremely warm waters. These data sets, plus metadata, are archived at the
NOAA's National Centers for Environmental Information (NCEI) and are free for
public access: surface meteorology from Kiritimati Island
(https://doi.org/10.7289/V51Z42H4); surface meteorology and some surface fluxes from
NOAA Ship Ronald H. Brown (https://doi.org/10.7289/V5SF2T80;
https://doi.org/10.7289/V58050VP)
Ship- and island-based soundings from the 2016 El Niño Rapid Response (ENRR) field campaign
As the 2015/2016 El Niño was gathering strength in late 2015,
scientists at the Earth System Research Laboratory's Physical Sciences
Division proposed and led the implementation of the National Oceanic and
Atmospheric Administration's (NOAA's) El Niño Rapid Response (ENRR) Field
Campaign. ENRR observations included wind and thermodynamic profiles of the
atmosphere over the near-equatorial eastern central Pacific Ocean, many of
which were collected from two field sites and transmitted in near-real time
for inclusion in global forecasting models. From 26 January to 28 March 2016,
twice-daily rawinsonde observations were made from Kiritimati (pronounced
Christmas) Island (2.0° N, 157.4° E; call sign CXENRR).
From 16 February to 16 March 2016, three to eight radiosondes were launched
each day from NOAA Ship Ronald H. Brown (allocated call sign WTEC)
as it travelled southeast from Hawaii to service Tropical Atmosphere Ocean
(TAO) buoys along longitudes 140 and 125° W and then north to San
Diego, California. Both the rapid and remote nature of these deployments
created particular difficulties in collecting and disseminating the
soundings; these are described together with the methods used to reprocess
the data after the field campaign finished. The reprocessed and lightly
quality-controlled data have been put into an easy-to-read text format,
qualifying them to be termed Level 2 soundings. They are archived and
freely available for public access at NOAA's National Centers for
Environmental Information (NCEI) in the form of two separate data sets: one
consisting of 125 soundings from Kiritimati (https://doi.org/10.7289/V55Q4T5K), the
other of 193 soundings from NOAA Ship Ronald H. Brown
(https://doi.org/10.7289/V5X63K15). Of the Kiritimati soundings, 94 % reached the
tropopause and 88 % reached 40 hPa, while 89 % of the ship's
soundings reached the tropopause and 87 % reached 40 hPa. The soundings
captured the repeated advance and retreat of the Intertropical Convergence
Zone (ITCZ) at Kiritimati, a variety of marine tropospheric environments
encountered by the ship, and lower-stratospheric features of the 2015–2016
QBO (quasi-biennial oscillation), all providing a rich view of the local
atmosphere's response to the eastern central Pacific's extremely warm waters
during the 2015/16 El Niño
Internet of Things for Environmental Sustainability and Climate Change
Our world is vulnerable to climate change risks such as glacier retreat, rising temperatures, more variable and intense weather events (e.g., floods, droughts, and frosts), deteriorating mountain ecosystems, soil degradation, and increasing water scarcity. However, there are big gaps in our understanding of changes in regional climate and how these changes will impact human and natural systems, making it difficult to anticipate, plan, and adapt to the coming changes. The IoT paradigm in this area can enhance our understanding of regional climate by using technology solutions, while providing the dynamic climate elements based on integrated environmental sensing and communications that is necessary to support climate change impacts assessments in each of the related areas (e.g., environmental quality and monitoring, sustainable energy, agricultural systems, cultural preservation, and sustainable mining). In the IoT in Environmental Sustainability and Climate Change chapter, a framework for informed creation, interpretation and use of climate change projections and for continued innovations in climate and environmental science driven by key societal and economic stakeholders is presented. In addition, the IoT cyberinfrastructure to support the development of continued innovations in climate and environmental science is discussed
An observational study of a shallow gravity current triggered by katabatic flow
Observations from a wind profiler and a meteorological tower are utilized to
study the evolution of a gravity current that passed over the Meteorological
Research Institute's (MRI) field site in Tsukuba, Japan. The gravity current
was created by katabatic flow originating on the mountainous slopes west of
the field site. The passage of the shallow current was marked by a
pronounced pressure disturbance and was accompanied by vertical circulations
seen in the tower and profiler data. Direct vertical-beam measurements are
difficult, especially at low heights during high-gradient events like
density currents. In this study vertical velocities from the profiler are
derived from the four oblique beams by use of the Minimizing the Variance of
the Differences (MVD) method. The vertical velocities derived from the MVD
method agree well with in situ vertical velocities measured by a sonic anemometer
on the tower.
The gravity current is analyzed with surface observations, the wind
profiler/RASS and tower-mounted instruments. Observations from the
profiler/RASS and the tower-mounted instruments illustrate the structure of
the gravity current in both wind and temperature fields. The profiler data
reveal that there were three regions of waves in the vertical velocity
field: lee-type waves, a solitary wave and Kelvin-Helmholtz waves. The
lee-type waves in the head region of the gravity current seem to have been
generated by the gravity current acting as an obstacle to prefrontal flow.
The solitary wave was formed from the elevated head of the gravity current
that separated from the feeder flow. Profiler vertical-motion observations
resolve this wave and enable us to classify it as a Benjamin-Davis-Ono (BDO)
type solitary wave. The ducting mechanism that enabled the solitary wave to
propagate is also revealed from the wind profiler/RASS measurements. The
combination of high-resolution instruments at the MRI site allow us to
develop a uniquely detailed picture of a shallow gravity current structure
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Modulation of equatorial Pacific westerly/easterly wind events by the Madden-Julian oscillation and convectively-coupled Rossby waves
Synoptic wind events in the equatorial Pacific strongly influence the El Niño/Southern Oscillation (ENSO) evolution. This paper characterizes the spatio-temporal distribution of Easterly (EWEs) and Westerly Wind Events (WWEs) and quantifies their relationship with intraseasonal and interannual large-scale climate variability. We unambiguously demonstrate that the Madden–Julian Oscillation (MJO) and Convectively-coupled Rossby Waves (CRW) modulate both WWEs and EWEs occurrence probability. 86 % of WWEs occur within convective MJO and/or CRW phases and 83 % of EWEs occur within the suppressed phase of MJO and/or CRW. 41 % of WWEs and 26 % of EWEs are in particular associated with the combined occurrence of a CRW/MJO, far more than what would be expected from a random distribution (3 %). Wind events embedded within MJO phases also have a stronger impact on the ocean, due to a tendency to have a larger amplitude, zonal extent and longer duration. These findings are robust irrespective of the wind events and MJO/CRW detection methods. While WWEs and EWEs behave rather symmetrically with respect to MJO/CRW activity, the impact of ENSO on wind events is asymmetrical. The WWEs occurrence probability indeed increases when the warm pool is displaced eastward during El Niño events, an increase that can partly be related to interannual modulation of the MJO/CRW activity in the western Pacific. On the other hand, the EWEs modulation by ENSO is less robust, and strongly depends on the wind event detection method. The consequences of these results for ENSO predictability are discussed