Scaling behavior of lidar-derived snow depth across the semi-arid Chilean Andes

<p>The seasonal melt of mountain snow-cover provides a vital source of freshwater for downstream systems, sustaining multiple productive uses, population needs, and unique ecosystems. In the semi-arid Andes Cordillera, the snowpack acts as a natural water reservoir, releasing spring snowmelt runoff that accounts for more than 60 % of the total annual streamflow. Hence, understanding and characterizing the spatial variability of snow over this large domain is critical for accurate hydrological predictions. We examine the probability density functions and the geostatistical structure of snow depth through variogram analysis, using terrestrial lidar scans acquired during two seasons (2018 and 2019). First, we compare the spatial patterns of snow depth near maximum accumulation at three experimental sites: (i) the Tascadero catchment (-31.26°N, 3270-3790 m a.s.l.), (ii) the Las Bayas experimental catchment (-33.31°N, 3218-4022 m a.s.l.); and (iii) the Valle Hermoso catchment (-36.91°N, 1449-2563 m a.s.l.). Second, we analyze the inter- and intra-annual variability of snow depth patterns in the Las Bayas catchment, where seven scans were acquired during seasons 2018 and 2019. </p><p>The comparison across sites reveals snow depth fractal behavior until a first omnidirectional scale break in the range 15-22 m for unvegetated areas, and a short-range fractal dimension spanning 2.5-2.65. In the woodland of Valle Hermoso, a much shorter (5 m) scale break and a larger short-range fractal dimension (2.73) are found. Secondary scale ranges and breaks spanning 62-125 m are found in all sites but Tascadero, where snow depth follows a bimodal distribution across the domain. In the Las Bayas domain, inter-annual consistency is found in snow scaling patterns, with two distinct regions separated by a short scale break ~6 m early in the winter, increasing to larger break lengths (15-18 m) in July and August. These results help to inform about the appropriate spatial configuration for snowpack modeling across the Andes. Efforts to better understand the modulation of topography (slope and wind exposure) and vegetation on snow depth distribution patterns, as well as impacts of dominant wind directions on anisotropies in fractal parameters, are ongoing.</p>

Crossover and peaks in the Pleistocene climate spectrum; understanding from simple ice age models

The power spectrum provides a compact representation of the scale dependence of the variability in time series. At multi-millennial time scales the spectrum of the Pleistocene climate is composed of a set of narrow band spectral modes attributed to the regularly varying changes in insolation from the astronomical change in Earth’s orbit and rotation superimposed on a continuous background generally attributed to stochastic variations. Quantitative analyses of paleoclimatic records indicate that the continuous part comprises a dominant part of the variance. It exhibits a power-law dependency typical of stochastic, self-similar processes, but with a scale break at the frequency of glacial-interglacial cycles. Here we discuss possible origins of this scale break, the connection between the continuous background and the narrow bands, and the apparently modest spectral power above the continuum at these scales. We demonstrate that the observed scale break around 100 ka can have a variety of different origins and does not imply an internal time scale of correlation as implied by the simplest linear stochastic model.

PELATIHAN AUTOCAD 2D UNTUK PEMUDA GAMPONG MESJID PUNTEUET KECAMATAN BLANG MANGAT KOTA LHOKSEUMAWE

Pelaksanaan kegiatan pelatihan AutoCAD bagi Pemuda Gampong Mesjid Punteuet Kecamatan Blang Mangat Kota Lhokseumawe bertujuan untuk membekali para Pemuda Gampong Mesjid Punteuet agar dapat mengoperasikan software AutoCAD dan mampu memmbuat gambar 2 dimensi dengan AutoCAD sebagai bekal untuk bisa mencari kerja setelah tamat SLTA atau kuliah. Khalayak sasaran dalam kegiatan ini adalah para Pemuda Gampong Mesjid Punteuet Kecamatan Blang Mangat Kota Lhokseumawe yang sedang sekolah SMA atau sederajat ataupun sudah tamat SMA dan yang sedang kuliah ataupun yang sudah tamat kuliah. Pelatihan ini dilaksanakan di Lab. Perancangan Jurusan Teknik Mesin Politeknik Buketrata Lhokseumawe, dengan jumlah peserta pelatihan sebanyak 10 orang, waktu pelatihan 2 (dua) minggu, mulai pukul 14.00 s/d 17.00. Para peserta dibekali dengan materi: Membuat sket gambar dengan perintah Line, Polyline, Polygon, Rectangle, Ellipse, Arc, Spline, Hatch, Gradiend dan Multyline Text. Memodifikasi gambar dengan perintah Delete, Copy, Mirror, Offset, Array, Move, Trim, Extend, scale, Break, Fillet dan Chamfer. Membuat dimensi pada gambar 2D dengan menggunakan perintah perintah Linear, Aligned, Radius, Diameter, Angular, Tolerance, dan Oblique. Mengelola file, membuat file baru, menyimpan file, dan plotter gambar ke printer. Kepada para peserta dilakukan evaluasi baik untuk teori maupun praktek untuk mengetahui tingkat kemampuan penyerapan materi yang diajarkan, diharapkan 80% dari peserta pelatihan telah dapat munguasai materi yang diajarkan. Setelah mengikuti pelatihan ini para pemuda Gampong Mesjid Punteuet memperoleh keterampilan sehingga mereka memiliki Life skill sebagai bekal terjun kelapangan kerja. Kata kunci: AutoCAD, Perancangan, Life skill, Gambar

Instantaneous variance scaling of AIRS profiles using a circular area Monte Carlo approach

Satellite observations are used to study the variance scaling of temperature and water vapor in the atmosphere. A high resolution of 13.5 km at nadir, instead of 45 km as in previous Atmospheric Infrared Sounder (AIRS) studies, enables the derivation of the variance-scaling exponents down to length scales of ~ 55 km.With the variable-size circular area Monte Carlo approach the exponents can be computed instantaneously along the track of Aqua, which gives more insight into the scaling behavior of the atmospheric variables in individual Level 2 satellite granules. Scaling exponents are shown to fluctuate heavily between β = −1 and β = −3 at the larger scales, while at the smaller scales they are often closer to β = −2, and they decrease a bit for moisture at the smallest scales that are considered. Outside the tropics, the temperature large-scale variance-scaling exponent is often close to −3 due to large temperature slopes that are present along the track of Aqua, likely as a result of geostrophic turbulence. Around the tropics, this exponent is often closer to −1, because the tropical atmosphere is dominated by smaller-scale processes such as moist convection, leading to an observable reverse scale break. In contrast, water vapor is shown to have large-scale exponents often close to −3 around the tropics, because there, large-scale water vapor slopes are common along the Aqua track. Furthermore, the scale-break length scale turns out to be highly variable and shows a large spread. The presented variance-scaling results are of importance for cloud parameterization purposes.

Scaling Analysis of Temperature and Liquid Water Content in the Marine Boundary Layer Clouds during POST

The authors have analyzed the scaling behavior of marine boundary layer (MBL) clouds using high-resolution temperature (T) and liquid water content (LWC) fluctuations from aircraft measurements collected over the Pacific Ocean during the Physics of Stratocumulus Top (POST) research campaign in summer of 2008. As an extension of the past studies for scale-invariant properties of MBL clouds, the authors studied the variability of scaling exponents with height. The results showed that both LWC and T have two distinct scaling regimes: the first one displays scale invariance over a range from about 1–5 m to at least 7 km, and the second one goes from about 0.1–1 to 1–5 m. For the large-scale regime (r > 1–5 m), turbulence in MBL clouds is multifractal, while scale break and scaling exponents vary with height, most significantly in the cloud-top region. For example, LWC spectral exponent β increases from 1.42 at cloud base to 1.58 at cloud top, while scale break decreases from ~5 m at cloud base to 0.8 m at cloud top. The bifractal parameters (H1, C1) for LWC increase from (0.14, 0.02) at cloud base to (0.33, 0.1) at cloud top while maintaining a statistically significant linear relationship C1 ≈ 0.4H1 − 0.04 in MBL clouds. From near surface to cloud top, (H1, C1) for T also increase with height, but above cloud top H1 increases and C1 decreases with height. The results suggest the existence of three turbulence regimes: near the surface, in the middle of the boundary layer, and in the cloud-top region, which need to be distinguished.

Are there multiple scaling regimes in Holocene temperature records?

The concept of multiple scaling regimes in temperature time series is examined, with emphasis on the question whether or not a monoscaling model with one single scaling regime can be rejected from observation data from the Holocene. A model for internal variability with only one regime is simpler and allows more certain predictions on timescales of centuries when combined with existing knowledge of radiative forcing. Our analysis of spectra from stable isotope ratios from Greenland and Antarctica ice cores shows that a scale break around centennial timescales is evident for the last glacial period, but not for the Holocene. Spectra from a number of late Holocene multiproxy temperature reconstructions, and one from the entire Holocene, have also been analysed, without identifying a significant scale break. Our results indicate that a single-regime scaling climate noise, with some non-scaling fluctuations on a millennial timescale superposed, cannot be rejected as a null model for the Holocene climate. The scale break observed from the glacial time ice-core records is likely caused by the influence of Dansgaard–Oeschger events and teleconnections to the Southern Hemisphere on centennial timescales. From our analysis we conclude that the two-regime model is not sufficiently justified for the Holocene to be used for temperature prediction on centennial timescales.

Are there multiple scaling regimes in Holocene temperature records?

The concept of multiple scaling regimes in temperature time series is examined, with emphasis on the question whether or not a mono-scaling model can be rejected from the data at hand. A model with only one regime is simpler and is preferred if this explains the observed variability. Our analysis of spectra from reconstructed air temperature from Greenland and Antarctica ice cores shows that a scale break around centennial time scales is evident for the last glacial period, but not for the Holocene. Nor by analysing a number of late Holocene multiproxy temperature reconstructions can a significant scale break be identified. Our results indicate that a mono-scaling model cannot be rejected as a null model for the Holocene climate up to at least millennial time scales, although it can be rejected for the glacial climate state. The scale break observed from the glacial time ice core records is likely caused by the influence of Dansgaard–Oeschger events and teleconnections to the Southern Hemisphere on centennial time scales. From our analysis we conclude that the two-regime model is not sufficiently justified for the Holocene to be used for temperature prediction on centennial time scales.

The Influence of Land Surface Heterogeneities on Cloud Size Development

This study analyzes the effects of land surface heterogeneities at various horizontal scales on the transition from shallow to deep convection and on the cloud size distribution. An idealized case of midlatitude summertime convection is simulated by means of large-eddy simulations coupled to an interactive land surface. The transition is accelerated over heterogeneous surfaces. The simulation with an intermediate patch size of 12.8 km exhibits the fastest transition with a transition time two-thirds that over a homogeneous surface. A similar timing is observed for the precipitation onset whereas the total accumulated rainfall tends to increase with patch size. The cloud size distribution can be approximated by a power law with a scale break. The exponent of the power law is independent of the heterogeneity scale, implying a similar cloud cover between the simulations. In contrast, the scale break varies with patch size. The size of the largest clouds does not scale with the boundary layer height, although their maximum size scales with the patch size. Finally, the idea that larger clouds grow faster, known from homogeneous surface conditions, is not fully valid over heterogeneous surfaces. These various aspects can be understood from the complex interplay between the characteristics of the triggered mesoscale circulations and a cloud development acting in response to the diurnal cycle in surface heating. The results also call for adequate representation of such effects in convective parameterizations.

Scale Dependency of Total Water Variance and Its Implication for Cloud Parameterizations

The scale dependency of variance of total water mixing ratio is explored by analyzing data from a general circulation model (GCM), a numerical weather prediction model (NWP), and large-eddy simulations (LESs). For clarification, direct numerical simulation (DNS) data are additionally included, but the focus is placed on defining a general scaling behavior for scales ranging from global down to cloud resolving. For this, appropriate power-law exponents are determined by calculating and approximating the power density spectrum. The large-scale models (GCM and NWP) show a consistent scaling with a power-law exponent of approximately −2. For the high-resolution LESs, the slope of the power density spectrum shows evidence of being somewhat steeper, although the estimates are more uncertain. Also the transition between resolved and parameterized scales in a current GCM is investigated. Neither a spectral gap nor a strong scale break is found, but a weak scale break at high wavenumbers cannot be excluded. The evaluation of the parameterized total water variance of a state-of-the-art statistical scheme shows that the scale dependency is underestimated by this parameterization. This study and the discovered general scaling behavior emphasize the need for a development of scale-dependent parameterizations.