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Nisam Mang Luxom
and
Rishi Kumar Sharma

Abstract

Large expanses of snow leopard habitat overlap with extensively used areas for livestock grazing. A fundamental question for conservationists is to determine whether livestock production can be reconciled with the conservation of rare and threatened large carnivores. Therefore, numerous studies focus on the relationship between carnivore densities and space use and environmental, anthropogenic, and topographic variables. Using snow leopard sign surveys in areas with high and low grazing disturbance, Hong et al. posit that livestock grazing directly impacts fine-scale habitat selection by snow leopards. The authors recommend controlling livestock grazing to help restore habitat complexity and alpine environment diversity. However, the approach by which Hong et al. have reached this conclusion is inadequate and is based on a methodology that fails to address the research question appropriately. We argue that 1) identification of a biologically relevant scale of study is the first essential step toward inferring carnivore–habitat relationships, 2) the authors draw inconsistent conclusions from their data on sign densities in high and low grazing disturbance areas, 3) ideally, the snow leopard–livestock relationship needs to be examined across a gradient of livestock grazing intensities and at multiple spatial scales, and 4) it is inappropriate to draw conclusions for landscape/regional scales from a study conducted at a finer and undefined scale. We suggest that future studies should clearly define the scale of the study, identify appropriate habitat variables of interest, and use meaningful measurement instruments to serve as proxies for variables of interest.

Free access
Zhiling Liao
,
Shaowu Li
,
Ye Liu
, and
Qingping Zou
Restricted access
Deepak Waman
,
Sachin Patade
,
Arti Jadav
,
Akash Deshmukh
,
Ashok Kumar Gupta
,
Vaughan T. J. Phillips
,
Aaron Bansemer
, and
Paul J. DeMott

Abstract

Various mechanisms of secondary ice production (SIP) cause multiplication of numbers of ice particle, after the onset of primary ice. A measure of SIP is the ice enhancement ratio (“IE ratio”) defined here as the ratio between number concentrations of total ice (excluding homogeneously nucleated ice) and active ice-nucleating particles (INPs). A convective line observed on 11 May 2011 over the Southern Great Plains in the Mesoscale Continental Convective Cloud Experiment (MC3E) campaign was simulated with the “Aerosol–Cloud” (AC) model. AC is validated against coincident MC3E observations by aircraft, ground-based instruments, and satellite. Four SIP mechanisms are represented in AC: the Hallett–Mossop (HM) process of rime splintering, and fragmentation during ice–ice collisions, raindrop freezing, and sublimation. The vertical profile of the IE ratio, averaged over the entire simulation, is almost uniform (102 to 103) because fragmentation in ice–ice collisions dominates at long time scales, driving the ice concentration toward a theoretical maximum. The IE ratio increases with both the updraft (HM process, fragmentation during raindrop freezing, and ice–ice collisions) and downdraft speed (fragmentation during ice–ice collisions and sublimation). As reported historically in aircraft sampling, IE ratios were predicted to peak near 103 for cloud-top temperatures close to the −12°C level, mostly due to the HM process in typically young clouds with their age less than 15 min. At higher altitudes with temperatures of −20° to −30°C, the predicted IE ratios were smaller, ranging from 10 to 102, and mainly resulted from fragmentation in ice–ice collisions.

Restricted access
Yang Hong
,
Thomas Connor
,
Huan Luo
,
Xiaoxing Bian
,
Zhaogang Duan
,
Zhuo Tang
, and
Jindong Zhang

Abstract

We thank Luxom and Sharma for their attention to and comments on our study. In recent years, livestock have been expanding into snow leopard habitat, and we conducted this study to examine the effects of that encroachment on snow leopard habitat within Wolong Nature Reserve. Specific responses to Luxom and Sharma’s comments include the following: 1) Many habitat factors influence carnivore–habitat relationships at varying spatial scales, and it is difficult for any single study to address the full suite of factors acting across all scales of selection. Given this fact and the limited spatial scale of our snow leopard sign survey, we mainly focused on snow leopard space use and microhabitat selection. 2) Our results are not necessarily conflicting, but more research is required to further explain how high sign densities, concentrated space use, and weak habitat selection behaviors might relate to each other. 3) We agree that examining a gradient of grazing intensities would be preferable, but because of the difficulty in collecting sufficient field data and the nature of livestock grazing patterns in our study area, we think that dividing our survey area into high- and low-grazing-disturbance areas was appropriate. 4) The original intent of this study was to examine habitat factors and response to livestock within our study area in Wolong Nature Reserve, and we did not intend for our specific results to be used for management recommendations beyond Wolong but instead encourage similar studies to be conducted in other areas.

Free access
Abhishek Kumar Jha
,
Subrata Kumar Das
,
U. V. Murali Krishna
, and
Sachin M. Deshpande

Abstract

This study investigates the diurnal cycle, propagation, and progression of convective storms (CSs) on the eastern edge of India’s monsoon trough (MT) using 9 years of S-band radar measurements with satellite and reanalysis datasets. CSs initiate over ocean during midnight–early morning hours and propagate onshore in succeeding hours. CSs exhibit two semidiurnal peaks, one during afternoon hours over inland areas and another during midnight–early morning hours in oceanic/coastal locations. The deep and intense afternoon peak over inland regions is attributed to land surface heating and associated destabilization. The weak and shallower but organized midnight–morning peak and propagation of CSs toward the coast are attributed to the nocturnal land breeze and its interaction with prevailing onshore flow. The observed lead–lag of a few hours in the diurnal cycle of different cumulus modes correspond to the transition of congestus into deep and then, often, into overshooting modes. Moisture budget analysis showed atmospheric regulation of this transition through thermodynamic (congestus moistening) and dynamic processes (vertical advection). Theoretical time scales were invoked to estimate the relative role of vertical advective versus congestus moistening for promoting the afternoon transition from congestus to deeper modes. Comparing the time scales for congestus moistening (18–46 h) and dynamics (3 h) with the actual transition time scales (2–4 h) reveal that congestus moistening is too slow to explain the observed lead–lag in CS modes. Though both thermodynamic and dynamic processes moisten the midlevel prior to deep/overshooting convection, vertical advection is the dominant dynamic process for the observed congestus–deep–overshooting transition.

Significance Statement

Tropical rainfall is usually linked with convection in the morning and afternoon hours. We look at the basic physical processes that lead to those convective activities peaks. The afternoon peak is linked to maximum heating, resulting in an unstable environment, whereas the morning peak is linked to the interaction of large-scale monsoon flow with a land breeze. Furthermore, daily solar heating visually shows a shallow-to-deep progression of convection. The moist midlevel environment was shown to precede such convective development in a day. The large-scale monsoon flow is a dominant cause of this moistening. The monsoon dynamic flow takes roughly 2–3 h to sufficiently moist shallow storms into deep storms, whereas the local thermodynamic moistening process takes about 18–46 h.

Restricted access
Manuel Tanguy
,
Gaëlle de Coëtlogon
, and
Laurence Eymard

Abstract

ERA5 reanalyses and observations of convective clouds and precipitation are used over the northern Gulf of Guinea between 7°W and 3°E to study the influence of ocean surface temperature and the land–sea temperature gradient on Guinea Coast rainfall (GCR) in boreal spring and summer. Seasonal composites are calculated around two dates indexing the onset (Tref) and demise (Tend) of the GCR. The Tref date corresponds to the emergence of the equatorial upwelling in boreal spring, which “pushes” the zonal precipitation belt northward against the Guinea coast. The Tend date characterizes the emergence of the coastal upwelling in July, which is known to coincide with the beginning of the “Little Dry Season” that lasts until September. Along the Guinea Coast, the diurnal cycle of the air–sea temperature gradient controls precipitation through the land–sea breeze, which explains why precipitation reaches its maximum around noon over the ocean, and in the late afternoon over the continent. The emergence of the Guinea Coast upwelling in July induces a weakening of southerlies on a seasonal scale, and a weaker land breeze on a diurnal scale. It induces a decrease in the convergence of humidity transport across the coast and in coastal oceanic precipitation. Therefore, the GCR is seasonally controlled by the latitude of the maximum tropospheric water vapor content and the annual cycle of the West African monsoon, but the ocean surface temperature is responsible for the abruptness of its onset via the intensification of the equatorial upwelling around the end of May, and possibly of its demise as well via the emergence of the coastal upwelling by early July.

Open access
Georgy E. Manucharyan
and
Andrew L. Stewart

Abstract

The Beaufort Gyre (BG) is hypothesized to be partially equilibrated by those mesoscale eddies that form via baroclinic instabilities of its currents. However, our understanding of the eddy field’s dependence on the mean BG currents and the role of sea ice remains incomplete. This theoretical study explores the scales and vertical structures of eddies forming specifically due to baroclinic instabilities of interior BG flows. An idealized quasigeostrophic model is used to show that flows driven only by the Ekman pumping contain no interior potential vorticity (PV) gradients and generate weak and large eddies, O(200)km in size, with predominantly barotropic and first baroclinic mode energy. However, flows containing realistic interior PV gradients in the Pacific halocline layer generate significantly smaller eddies of about 50 km in size, with a distinct second baroclinic mode structure and a subsurface kinetic energy maximum. The dramatic change in eddy characteristics is shown to be caused by the stirring of interior PV gradients by large-scale barotropic eddies. The sea ice–ocean drag is identified as the dominant eddy dissipation mechanism, leading to realistic subsurface maxima of eddy kinetic energy for drag coefficients higher than about 2 × 10−3. A scaling law is developed for the eddy potential enstrophy, demonstrating that it is directly proportional to the interior PV gradient and the square root of the barotropic eddy kinetic energy. This study proposes a possible formation mechanism of large BG eddies and points to the importance of accurate representation of the interior PV gradients and eddy dissipation by ice–ocean drag in BG simulations and theory.

Open access
Sebastian Borchert
and
Günther Zängl

Abstract

Parameterizations of subgrid-scale gravity waves (GWs) in atmospheric models commonly involve the description of the dissipation of GWs. Where they dissipate, GWs have an increased effect on the large-scale flow. Instabilities that trigger wave breaking are an important starting point for the route to dissipation. Possible destabilizing mechanisms are numerous, but the classical vertical static instability is still regarded as a key indicator for the disposition to wave breaking. In this work, we investigate how the horizontal variations associated with a GW could alter the criterion for static instability. To this end, we use an extension of the common parcel displacement method. This three-dimensional static stability analysis predicts a significantly larger range of instability than does the vertical static stability analysis. In this case, the Lindzen-type saturation adjustment to a state of marginal stability is perhaps a less suitable ansatz for the parameterization of the GW breaking. To develop a possible ansatz for the GW dissipation due to three-dimensional instability, we apply the methods of irreversible thermodynamics, which are embedded in the Gibbs formalism of dynamics. In this way, the parameterization does not only satisfy the second law of thermodynamics, but it can also be made consistent with the conservation of energy and further (non-)conservation principles. We develop the parameterization for a discrete spectrum of GW packets. Offline computations of GW drag and dissipative heating rates are performed for two vertical profiles of zonal wind and temperature for summer and winter conditions from CIRA data. The results are compared to benchmarks from the literature.

Restricted access
Chunying Liu
,
Eric Freeman
,
Elizabeth C. Kent
,
David I. Berry
,
Steven J. Worley
,
Shawn R. Smith
,
Boyin Huang
,
Huai-min Zhang
,
Thomas Cram
,
Zaihua Ji
,
Mathieu Ouellet
,
Isabelle Gaboury
,
Frank Oliva
,
Axel Andersson
,
William E. Angel
,
Angela R. Sallis
, and
Adedoja Adeyeye

Abstract

This paper describes the new International Comprehensive Ocean–Atmosphere Data Set (ICOADS) near-real-time (NRT) release (R3.0.2), with greatly enhanced completeness over the previous version (R3.0.1). R3.0.1 had been operationally produced monthly from January 2015 onward, with input data from the World Meteorological Organization (WMO) Global Telecommunication Systems (GTS) transmissions in the Traditional Alphanumeric Codes (TAC) format. Since the release of R3.0.1, however, many observing platforms have changed, or are in the process of transitioning, to the Binary Universal Form for Representation of Meteorological Data (BUFR) format. R3.0.2 combines input data from both BUFR and TAC formats. In this paper, we describe input data sources; the BUFR decoding process for observations from drifting buoys, moored buoys, and ships; and the data quality control of the TAC and BUFR data streams. We also describe how the TAC and BUFR streams were merged to upgrade R3.0.1 into R3.0.2 with duplicates removed. Finally, we compare the number of reports and spatial coverage of essential climate variables (ECVs) between R3.0.1 and R3.0.2. ICOADS NRT R3.0.2 shows both quantitative and qualitative gains from the inclusion of BUFR reports. The number of observations in R3.0.2 increased by nearly 1 million reports per month, and the coverage of buoy and ship sea surface temperatures (SSTs) on monthly 2° × 2° grids increased by 20%. The number of reported ECVs also increased in R3.0.2. For example, observations of SST and sea level pressure (SLP) increased by around 30% and 20%, respectively, as compared to R3.0.1, and salinity is a new addition to the ICOADS NRT product in R3.0.2.

Significance Statement

The International Comprehensive Ocean–Atmosphere Data Set (ICOADS) is the largest collection of surface marine observations spanning from 1662 to the present. A new version, ICOADS near-real-time 3.0.2, includes data transmitted in the Binary Universal Form for Representation of Meteorological Data (BUFR) format, in combination with Traditional Alphanumeric Codes (TAC) data. Many of the organizations that report observations in near–real time have moved to BUFR, so this update brings ICOADS into alignment with collections and archives of these international data distributions. By including the BUFR reports, the number of observations in the upgraded version of ICOADS increased by nearly one million reports per month and spatial coverage of buoy and ship SSTs increased by 20% over the previous version.

Open access
C. A. Luecke
,
H. W. Wijesekera
,
E. Jarosz
,
D. W. Wang
,
T. G. Jensen
,
S.U.P. Jinadasa
,
H. J. S. Fernando
, and
W. J. Teague

Abstract

The formation of a sharp oceanic front located south-southeast of Sri Lanka during the southwest monsoon is examined through in-situ and remote observations, and high-resolution model output. Remote-sensing and model output reveal that the front extends approximately 200 km eastward from the southeast coast of Sri Lanka toward the southern Bay of Bengal (BoB). This annually occurring front is associated with the boundary between the southwest-monsoon current with high-salinity water to the south, and a weak-flow field comprised of relatively-fresh BoB water to the north. The front contains a line of high chlorophyll extending from the coastal-upwelling zone, often for several-hundred kilometers. Elevated turbulent diffusivities ~10−2 m2 s−1 along with large diapycnal fluxes of heat and salt were found within the front. The formation of the front and vertical transports are linked to local wind-stress curl. Large vertical velocities (~50 m d−1) indicate the importance of ageostropic, submesoscale processes. To examine these processes, the Ertel potential vorticity (PV) was computed using the observations and numerical model output. The model output shows a ribbon of negative PV along the front between the coastal upwelling zone and two eddies (Sri Lanka Dome and an anticyclonic eddy) typically found in the southern BoB. PV estimates support the view that the flow is susceptible to submesoscale instabilities, which in turn generate high vertical velocities within the front. Frontal upwelling and heightened mixing show that the seasonal front is regionally important to linking the fresh surface water of the BoB with the Arabian Sea.

Restricted access