Atmospheric Moisture Budget and Spatial Resolution Dependence of Precipitation Extremes in Aquaplanet Simulations

Abstract This study investigates the moisture budgets and resolution dependency of precipitation extremes in an aquaplanet framework based on the Community Atmosphere Model, version 4 (CAM4). Moisture budgets from simulations using two different dynamical cores, the Model for Prediction Across Scales-Atmosphere (MPAS-A) and High Order Method Modeling Environment (HOMME), but the same physics parameterizations suggest that during precipitation extremes the intensity of precipitation is approximately balanced by the vertical advective moisture transport. The resolution dependency in extremes from simulations at their native grid resolution originates from that of vertical moisture transport, which is mainly explained by changes in dynamics (related to vertical velocity ω) with resolution. When assessed at the same grid scale by area-weighted averaging the fine-resolution simulations to the coarse grids, simulations with either dynamical core still demonstrate resolution dependency in extreme precipitation with no convergence over the tropics, but convergence occurs at a wide range of latitudes over the extratropics. The use of lower temporal frequency data (i.e., daily vs 6 hourly) reduces the resolution dependency. Although thermodynamic (moisture) changes become significant in offsetting the effect of dynamics when assessed at the same grid scale, especially over the extratropics, changes in dynamics with resolution are still large and explain most of the resolution dependency during extremes. This suggests that the effects of subgrid-scale variability of ω and vertical moisture transport during extremes are not adequately parameterized by the model at coarse resolution. The aquaplanet framework and analysis described in this study provide an important metric for assessing sensitivities of cloud parameterizations to spatial resolution and dynamical cores under extreme conditions.

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Thermodynamic and Dynamic Mechanisms for Hydrological Cycle Intensification over the Full Probability Distribution of Precipitation Events

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-18-0067.1 ◽

2019 ◽

Vol 76 (2) ◽

pp. 497-516 ◽

Cited By ~ 15

Author(s):

Gang Chen ◽

Jesse Norris ◽

J. David Neelin ◽

Jian Lu ◽

L. Ruby Leung ◽

...

Keyword(s):

Probability Distribution ◽

Moisture Transport ◽

Large Scale ◽

Hydrological Cycle ◽

Dynamic Effect ◽

Hadley Cell ◽

Precipitation Extremes ◽

Specific Humidity ◽

Wide Range ◽

Full Probability

Abstract Precipitation changes in a warming climate have been examined with a focus on either mean precipitation or precipitation extremes, but changes in the full probability distribution of precipitation have not been well studied. This paper develops a methodology for the quantile-conditional column moisture budget of the atmosphere for the full probability distribution of precipitation. Analysis is performed on idealized aquaplanet model simulations under 3-K uniform SST warming across different horizontal resolutions. Because the covariance of specific humidity and horizontal mass convergence is much reduced when conditioned onto a given precipitation percentile range, their conditional averages yield a clear separation between the moisture (thermodynamic) and circulation (dynamic) effects of vertical moisture transport on precipitation. The thermodynamic response to idealized climate warming can be understood as a generalized “wet get wetter” mechanism, in which the heaviest precipitation of the probability distribution is enhanced most from increased gross moisture stratification, at a rate controlled by the change in lower-tropospheric moisture rather than column moisture. The dynamic effect, in contrast, can be interpreted by shifts in large-scale atmospheric circulations such as the Hadley cell circulation or midlatitude storm tracks. Furthermore, horizontal moisture advection, albeit of secondary role, is important for regional precipitation change. Although similar mechanisms are at play for changes in both mean precipitation and precipitation extremes, the thermodynamic contributions of moisture transport to increases in high percentiles of precipitation tend to be more widespread across a wide range of latitudes than increases in the mean, especially in the subtropics.

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Generalized Heterodyne Configurations for Photo-induced Force Microscopy

10.26434/chemrxiv.9633407 ◽

2019 ◽

Author(s):

Le Wang ◽

Devon Jakob ◽

Haomin Wang ◽

Alexis Apostolos ◽

Marcos M. Pires ◽

...

Keyword(s):

Spatial Resolution ◽

Repetition Rate ◽

Modulation Frequency ◽

High Harmonic ◽

Chemical Imaging ◽

Heterodyne Detection ◽

Force Microscopy ◽

Wide Range ◽

The Difference ◽

Afm Cantilever

<div>Infrared chemical microscopy through mechanical probing of light-matter interactions by atomic force microscopy (AFM) bypasses the diffraction limit. One increasingly popular technique is photo-induced force microscopy (PiFM), which utilizes the mechanical heterodyne signal detection between cantilever mechanical resonant oscillations and the photo induced force from light-matter interaction. So far, photo induced force microscopy has been operated in only one heterodyne configuration. In this article, we generalize heterodyne configurations of photoinduced force microscopy by introducing two new schemes: harmonic heterodyne detection and sequential heterodyne detection. In harmonic heterodyne detection, the laser repetition rate matches integer fractions of the difference between the two mechanical resonant modes of the AFM cantilever. The high harmonic of the beating from the photothermal expansion mixes with the AFM cantilever oscillation to provide PiFM signal. In sequential heterodyne detection, the combination of the repetition rate of laser pulses and polarization modulation frequency matches the difference between two AFM mechanical modes, leading to detectable PiFM signals. These two generalized heterodyne configurations for photo induced force microscopy deliver new avenues for chemical imaging and broadband spectroscopy at ~10 nm spatial resolution. They are suitable for a wide range of heterogeneous materials across various disciplines: from structured polymer film, polaritonic boron nitride materials, to isolated bacterial peptidoglycan cell walls. The generalized heterodyne configurations introduce flexibility for the implementation of PiFM and related tapping mode AFM-IR, and provide possibilities for additional modulation channel in PiFM for targeted signal extraction with nanoscale spatial resolution.</div>

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Status of Phenological Research Using Sentinel-2 Data: A Review

Remote Sensing ◽

10.3390/rs12172760 ◽

2020 ◽

Vol 12 (17) ◽

pp. 2760

Author(s):

Gourav Misra ◽

Fiona Cawkwell ◽

Astrid Wingler

Keyword(s):

Vegetation Index ◽

Temporal Frequency ◽

Short Wave ◽

Current State ◽

Red Edge ◽

Natural Grasslands ◽

Wide Range ◽

Normalised Difference Vegetation Index ◽

Satellite Sensors ◽

Sentinel 2

Remote sensing of plant phenology as an indicator of climate change and for mapping land cover has received significant scientific interest in the past two decades. The advancing of spring events, the lengthening of the growing season, the shifting of tree lines, the decreasing sensitivity to warming and the uniformity of spring across elevations are a few of the important indicators of trends in phenology. The Sentinel-2 satellite sensors launched in June 2015 (A) and March 2017 (B), with their high temporal frequency and spatial resolution for improved land mapping missions, have contributed significantly to knowledge on vegetation over the last three years. However, despite the additional red-edge and short wave infra-red (SWIR) bands available on the Sentinel-2 multispectral instruments, with improved vegetation species detection capabilities, there has been very little research on their efficacy to track vegetation cover and its phenology. For example, out of approximately every four papers that analyse normalised difference vegetation index (NDVI) or enhanced vegetation index (EVI) derived from Sentinel-2 imagery, only one mentions either SWIR or the red-edge bands. Despite the short duration that the Sentinel-2 platforms have been operational, they have proved their potential in a wide range of phenological studies of crops, forests, natural grasslands, and other vegetated areas, and in particular through fusion of the data with those from other sensors, e.g., Sentinel-1, Landsat and MODIS. This review paper discusses the current state of vegetation phenology studies based on the first five years of Sentinel-2, their advantages, limitations, and the scope for future developments.

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Scale dependence of cirrus heterogeneity effects. Part II: MODIS NIR and SWIR channels

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-12105-2018 ◽

2018 ◽

Vol 18 (16) ◽

pp. 12105-12121 ◽

Cited By ~ 4

Author(s):

Thomas Fauchez ◽

Steven Platnick ◽

Tamás Várnai ◽

Kerry Meyer ◽

Céline Cornet ◽

...

Keyword(s):

Radiative Transfer ◽

Spatial Resolution ◽

Thermal Infrared ◽

Radiative Effects ◽

Ice Clouds ◽

Plane Parallel ◽

Wide Range ◽

The Impact ◽

Side Illumination

Abstract. In a context of global climate change, the understanding of the radiative role of clouds is crucial. On average, ice clouds such as cirrus have a significant positive radiative effect, but under some conditions the effect may be negative. However, many uncertainties remain regarding the role of ice clouds on Earth's radiative budget and in a changing climate. Global satellite observations are particularly well suited to monitoring clouds, retrieving their characteristics and inferring their radiative impact. To retrieve ice cloud properties (optical thickness and ice crystal effective size), current operational algorithms assume that each pixel of the observed scene is plane-parallel and homogeneous, and that there is no radiative connection between neighboring pixels. Yet these retrieval assumptions are far from accurate, as real radiative transfer is 3-D. This leads to the plane-parallel and homogeneous bias (PPHB) plus the independent pixel approximation bias (IPAB), which impacts both the estimation of top-of-the-atmosphere (TOA) radiation and the retrievals. An important factor that determines the impact of these assumptions is the sensor spatial resolution. High-spatial-resolution pixels can better represent cloud variability (low PPHB), but the radiative path through the cloud can involve many pixels (high IPAB). In contrast, low-spatial-resolution pixels poorly represent the cloud variability (high PPHB), but the radiation is better contained within the pixel field of view (low IPAB). In addition, the solar and viewing geometry (as well as cloud optical properties) can modulate the magnitude of the PPHB and IPAB. In this, Part II of our study, we simulate TOA 0.86 and 2.13 µm solar reflectances over a cirrus uncinus scene produced by the 3DCLOUD model. Then, 3-D radiative transfer simulations are performed with the 3DMCPOL code at spatial resolutions ranging from 50 m to 10 km, for 12 viewing geometries and nine solar geometries. It is found that, for simulated nadir observations taken at resolution higher than 2.5 km, horizontal radiation transport (HRT) dominates biases between 3-D and 1-D reflectance calculations, but these biases are mitigated by the side illumination and shadowing effects for off-zenith solar geometries. At resolutions coarser than 2.5 km, PPHB dominates. For off-nadir observations at resolutions higher than 2.5 km, the effect that we call THEAB (tilted and homogeneous extinction approximation bias) due to the oblique line of sight passing through many cloud columns contributes to a large increase of the reflectances, but 3-D radiative effects such as shadowing and side illumination for oblique Sun are also important. At resolutions coarser than 2.5 km, the PPHB is again the dominant effect. The magnitude and resolution dependence of PPHB and IPAB is very different for visible, near-infrared and shortwave infrared channels compared with the thermal infrared channels discussed in Part I of this study. The contrast of 3-D radiative effects between solar and thermal infrared channels may be a significant issue for retrieval techniques that simultaneously use radiative measurements across a wide range of solar reflectance and infrared wavelengths.

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Spatio-Temporal Super-Resolution Land Cover Mapping Based on Fuzzy C-Means Clustering

Remote Sensing ◽

10.3390/rs10081212 ◽

2018 ◽

Vol 10 (8) ◽

pp. 1212 ◽

Cited By ~ 4

Author(s):

Xiaohong Yang ◽

Zhong Xie ◽

Feng Ling ◽

Xiaodong Li ◽

Yihang Zhang ◽

...

Keyword(s):

Land Cover ◽

Spatial Pattern ◽

Spatial Resolution ◽

Super Resolution ◽

Land Cover Mapping ◽

Fuzzy C Means Clustering ◽

Land Cover Map ◽

Spatio Temporal ◽

Fine Resolution ◽

Land Cover Maps

Super-resolution land cover mapping (SRM) is a method that aims to generate land cover maps with fine spatial resolutions from the original coarse spatial resolution remotely sensed image. The accuracy of the resultant land cover map produced by existing SRM methods is often limited by the errors of fraction images and the uncertainty of spatial pattern models. To address these limitations in this study, we proposed a fuzzy c-means clustering (FCM)-based spatio-temporal SRM (FCM_STSRM) model that combines the spectral, spatial, and temporal information into a single objective function. The spectral term is constructed with the FCM criterion, the spatial term is constructed with the maximal spatial dependence principle, and the temporal term is characterized by the land cover transition probabilities in the bitemporal land cover maps. The performance of the proposed FCM_STSRM method is assessed using data simulated from the National Land Cover Database dataset and real Landsat images. Results of the two experiments show that the proposed FCM_STSRM method can decrease the influence of fraction errors by directly using the original images as the input and the spatial pattern uncertainty by inheriting land cover information from the existing fine resolution land cover map. Compared with the hard classification and FCM_SRM method applied to mono-temporal images, the proposed FCM_STSRM method produced fine resolution land cover maps with high accuracy, thus showing the efficiency and potential of the novel approach for producing fine spatial resolution maps from coarse resolution remotely sensed images.

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Orthopteran DCMD neuron: a reevaluation of responses to moving objects. I. Selective responses to approaching objects

Journal of Neurophysiology ◽

10.1152/jn.1992.68.5.1654 ◽

1992 ◽

Vol 68 (5) ◽

pp. 1654-1666 ◽

Cited By ~ 147

Author(s):

F. C. Rind ◽

P. J. Simmons

Keyword(s):

Moving Objects ◽

Temporal Frequency ◽

Angular Acceleration ◽

Spike Rate ◽

Single Peak ◽

Wide Field ◽

Movement Detector ◽

Star Wars ◽

Wide Range ◽

Real Objects

1. The "descending contralateral movement detector" (DCMD) neuron in the locust has been challenged with a variety of moving stimuli, including scenes from a film (Star Wars), moving disks, and images generated by computer. The neuron responds well to any rapid movement. For a dark object moving along a straight path at a uniform velocity, the DCMD gives the strongest response when the object travels directly toward the eye, and the weakest when the object travels away from the eye. Instead of expressing selectivity for movements of small rather than large objects, the DCMD responds preferentially to approaching objects. 2. The neuron shows a clear selectivity for approach over recession for a variety of sizes and velocities of movement both of real objects and in simulated movements. When a disk that subtends > or = 5 degrees at the eye approaches the eye, there are two peaks in spike rate: one immediately after the start of movement; and a second that builds up during the approach. When a disk recedes from the eye, there is a single peak in response as the movement starts. There is a good correlation between spike rate and angular acceleration of the edges of the image over the eye. 3. When an object approaches from a distance sufficient for it to subtend less than one interommatidial angle at the start of its approach, there is a single peak in response. The DCMD tracks the approach, and, if the object moves at 1 m/s or faster, the spike rate increases throughout the duration of object movement. The size of the response depends on the speed of approach. 4. It is unlikely that the DCMD encodes the time to collision accurately, because the response depends on the size as well as the velocity of an approaching object. 5. Wide-field movements suppress the response to an approaching object. The suppression varies with the temporal frequency of the background pattern. 6. Over a wide range of contrasts of object against background, the DCMD gives a stronger response to approaching than to receding objects. For low contrasts, the selectivity is greater for objects that are darker than the background than for objects that are lighter.

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Airborne fine-resolution UHF radar: an approach to the study of englacial reflections, firn compaction and ice attenuation rates

Journal of Glaciology ◽

10.3189/2015jog14j089 ◽

2015 ◽

Vol 61 (225) ◽

pp. 89-100 ◽

Cited By ~ 12

Author(s):

Cameron Lewis ◽

Sivaprasad Gogineni ◽

Fernando Rodriguez-Morales ◽

Ben Panzer ◽

Theresa Stumpf ◽

...

Keyword(s):

Dynamic Range ◽

High Sensitivity ◽

Ultra Wideband ◽

West Antarctica ◽

Ice Shelves ◽

Ross Ice Shelf ◽

Transmission Coefficients ◽

Ice Surface ◽

Wide Range ◽

Fine Resolution

AbstractWe have built and operated an ultra-wideband UHF pulsed-chirp radar for measuring firn stratigraphy from airborne platforms over the ice sheets of Greenland and West Antarctica. Our analysis found a wide range of capabilities, including imaging of post firn–ice transition horizons and sounding of shallow glaciers and ice shelves. Imaging of horizons to depths exceeding 600 m was possible in the colder interior regions of the ice sheet, where scattering from the ice surface and inclusions was minimal. The radar’s high sensitivity and large dynamic range point to loss tangent variations as the dominant mechanism for these englacial reflective horizons. The radar is capable of mapping interfaces with reflection coefficients as low as −80 dB near the firn–ice transition and as low as −64 dB at depths of 600 m. We found that firn horizon reflectivity strongly mirrored density variance, a result of the near-unity interfacial transmission coefficients. Zones with differing compaction mechanisms were also apparent in the data. We were able to sound many ice shelves and areas of shallow ice. We estimated ice attenuation rates for a few locations, and our attenuation estimates for the Ross Ice Shelf, West Antarctica, appear to agree well with earlier reported results.

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Parasitic infection and chronic energy deficiency in adults

Parasitology ◽

10.1017/s0031182000075582 ◽

1993 ◽

Vol 107 (S1) ◽

pp. S159-S167 ◽

Cited By ~ 9

Author(s):

P. S. Shetty ◽

N. Shetty

Keyword(s):

Nutritional Status ◽

Health Workers ◽

Parasitic Infection ◽

Critical Determinant ◽

Energy Deficiency ◽

Chronic Energy Deficiency ◽

Wide Range ◽

The Individual ◽

The Tropics ◽

Relationship Of

Interactions between infection and nutrition have been well recognized for several years now since they contribute directly to the health of individuals and communities. Malnourished individuals are specially prone to developing infections while infections themselves can lead to profound changes in the nutritional status of the individual. Health workers in developing countries in the tropics have long recognized the mutually aggravating interactions of malnutrition and infection. The importance of this synergistic relationship between infection and nu-tritional status has been studied extensively in the case of young children. The nutritional status of a young child is a critical determinant of both c morbidity and mortality resulting from a wide range of infections: bacterial, viral, or parasitic. Chandra (1983), in his review on the relationship of nutrition, immunity and infection has categorized the wide range of infectious agents (bacterial, viral, fungal and parasitic) into those that are definitely, variably or minimally influenced by the nutritional status of the child.

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Land–atmosphere interactions in the tropics

10.5194/hess-2019-12 ◽

2019 ◽

Author(s):

Pierre Gentine ◽

Adam Massmann ◽

Benjamin R. Lintner ◽

Sayed Hamed Alemohammad ◽

Rong Fu ◽

...

Keyword(s):

Land Surface ◽

Deep Convection ◽

Lower Troposphere ◽

Surface Fluxes ◽

Surface Radiation ◽

Spatial And Temporal Scales ◽

Wide Range ◽

Shallow Clouds ◽

The Tropics ◽

The Impact

Abstract. The continental tropics play a leading role in the terrestrial water and carbon cycles. Land–atmosphere interactions are integral in the regulation of surface energy, water and carbon fluxes across multiple spatial and temporal scales over tropical continents. We review here some of the important characteristics of tropical continental climates and how land–atmosphere interactions regulate them. Along with a wide range of climates, the tropics manifest a diverse array of land–atmosphere interactions. Broadly speaking, in tropical rainforests, light and energy are typically more limiting than precipitation and water supply for photosynthesis and evapotranspiration; whereas in savanna and semi-arid regions water is the critical regulator of surface fluxes and land–atmosphere interactions. We discuss the impact of the land surface, how it affects shallow clouds and how these clouds can feedback to the surface by modulating surface radiation. Some results from recent research suggest that shallow clouds may be especially critical to land–atmosphere interactions as these regulate the energy budget and moisture transport to the lower troposphere, which in turn affects deep convection. On the other hand, the impact of land surface conditions on deep convection appear to occur over larger, non-local, scales and might be critically affected by transitional regions between the climatologically dry and wet tropics.

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Inferred predation of Fairy Tern eggs by Ruddy Turnstones at Rottnest Island, Western Australia, an internationally significant shorebird site

10.20938/afo38115117 ◽

2021 ◽

Vol 38 ◽

pp. 115-117

Author(s):

C.N. Greenwell ◽

◽

Keyword(s):

Biodiversity Conservation ◽

Western Australia ◽

Breeding Success ◽

Behavioural Response ◽

Environment Protection ◽

Egg Predation ◽

Breeding Colony ◽

Wide Range ◽

Collective Group ◽

The Tropics

Ruddy Turnstones Arenaria interpres have been identified as egg-predators at seabird and shorebird colonies, including gull and tern colonies in the tropics and Northern Hemisphere. The Australian Fairy Tern Sternula nereis nereis is a threatened (Environment Protection and Biodiversity Conservation Act 1999: Vulnerable) coastal seabird, whose breeding behaviour and ecology expose it to a wide range of threats. This study describes inferred predation on Fairy Tern eggs at a small breeding colony on Rottnest Island, Western Australia, by Ruddy Turnstones, a previously unsuspected predator for thisspecies. Unlike the behavioural response shown towards Silver Gulls Larus novaehollandiae and Australian Ravens Corvus coronoides, which includes collective group defence and dive-bombing, Fairy Terns showed a lack of aggression towards Turnstones within the colony. The lack of a behavioural response suggests that the Terns did not recognise the Turnstones as predators, which may increase the risk of egg-predation. This study suggests that we should be alert to threats from unsuspected predators, which have the potential to reduce the breeding success of this Vulnerable tern.

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