Magnetic Field Intensity Modification to Force Free Model of Magnetic Clouds: Website of Wind Examples From Launch to July of 2015

We describe a new NASA website that shows normalized magnetic field (B) magnitude profiles within Wind magnetic clouds (MCs) (i.e., observations versus basic model versus modified model) for 209 MCs observed from launch in late 1994 to July of 2015, where model modification is based on the studies of Lepping et al. (Solar Phys, 2017, 292:27) and Lepping et al. (Solar Phys, 2018, 293:162); the basic force free magnetic cloud parameter fitting model employing Bessel functions (Lepping et al., J. Geophys. Res., 1990, 95:11957) is called the LJB model here. The fundamental principles should be applicable to the B-data from any spacecraft at 1 AU. Earlier (in the LJB study), we justified why the field magnitude can be thought of as decoupled from the field direction within an MC, and further, we justified this idea in terms of actual observations seen over a few decades with examples of MCs from Wind data. The model modification is achieved by adding a correction (“Quad”) value to the LJB model (Bessel function) value in the following manner: B (est)/B0 ≈ [LJB Model + Quad (CA,u)], where B0 is the LJB-estimated field magnitude value on the MC’s axis, CA is the relative closest approach (See Supplementary Appendix A), and u is the distance that the spacecraft travels through the MC from its entrance point. In an average sense, the Quad technique is shown to be successful for 82% of the past modeled MCs, when Quality (Q0) is good or excellent (see Supplementary Appendix A). The Quad technique is successful for 78% of MCs when all cases are considered. So Q0 of the MC LJB-fit is not a big factor when the success of the Quad scheme is considered. In addition, it is found that the Quad technique does not work better for MC events with higher solar wind speed. Yearly occurrence frequency of all MC events (NYearly) and those MC events with ΔσN/σN2 ≥ 0.5 (NΔσN/σN2≥0.5) are well correlated, but there is no solar cycle dependence for normalizing NΔσN/σN2≥0.5 with NYearly.

Angular Calibration of Visible and Infrared Binocular All-Sky-View Cameras Using Sun Positions

Visible and infrared binocular all-sky-view cameras can provide continuous and complementary ground-based cloud observations. Accurate angular calibration for every pixel is an essential premise to further cloud analysis and georeferencing. However, most current calibration methods mainly rely on calibration plates, which still remains difficult for simultaneously calibrating visible and infrared binocular cameras, especially with different imaging resolutions. Thus, in this study, we present a simple and convenient angular calibration method for wide field-of-view visible and infrared binocular cameras. Without any extra instruments, the proposed method only utilizes the relation between the angular information of direct sun lights and the projected sun pixel coordinates to compute the geometric imaging parameters of the two cameras. According to the obtained parameters, the pixel-view-angle for the visible and infrared all-sky images is efficiently computed via back projection. Meanwhile, the projected pixel coordinates for the incident lights at any angle can also be computed via reprojection. Experimental results show the effectiveness and accuracy of the proposed angular calibration through the error estimation of reprojection and back projection. As a novel application, we successfully achieve visible and infrared binocular image registration at the pixel level after finishing angular calibration, which not only verifies the accuracy of calibration results, but also contributes to further cloud parameter analysis under these two different imaging features. The registration results, to our knowledge, also provide a reference for the current blank in visible and infrared binocular cloud image registration.

Radial and circular motion of photons and test particles in the Schwarzschild black hole with quintessence and string clouds

The null and timelike geodesic motion in the vicinity of the Schwarzschild black hole in the presence of the string cloud parameter a and the quintessence field parameter q is studied. The ranges for both the parameters a and q are determined, which allow the existence of the black hole. In the radial motion of photon, the coordinate time t first decreases with the increasing values of both the parameters a and q and then in the close proximity of the horizon of the black hole, there is a turning point, after which the effect of the quintessence field is just opposite on the time t. For the massive particles, the proper time $$\tau $$ τ decreases with increasing values of the parameter a and increases with increase in the value of the parameter q. In the same case of the massive particles, the coordinate time t decreases with increase in the values of both the parameters a and q. Further, it is found that for test particles, the stable circular orbits exist in this spacetime for small values of both the parameters i.e., for $$0<a\ll 1$$ 0 < a ≪ 1 and $$0<q\ll 1$$ 0 < q ≪ 1 . It is observed that the radii of the null circular orbits increase as the values of the parameters a and q increase. While in the case of the timelike geodesics, the radii of the circular orbits increase as the value of the parameter a increases, and they decrease as the value of the parameter q increases.

Effects of the external string cloud on the Van der Waals-like behavior and efficiency of AdS-Schwarzschild black holes in massive gravity

In this paper, we study AdS-Schwarzschild black holes in four and five dimensions in dRGT minimally coupled to a cloud of strings. It is observed that the entropy of the string cloud and massive terms does not affect the black hole entropy. The observations about four dimensions indicate that the massive term in the presence of external string cloud cannot exhibit Van der Waals-like behavior for AdS-Schwarzschild black holes and, therefore there is only the Hawking–Page phase transition. In contrast, in five dimensions, the graviton mass modifies this behavior through the third massive term, so that a critical behavior and second-order phase transition is deduced. Also, the Joule–Thomson effect is not observed. The black hole stability conditions are also studied in four and five dimensions and a critical value for the string cloud parameter is presented. In five dimensions a degeneracy between states for extremal black holes is investigated. After studying black holes as thermodynamic systems, we consider such systems as heat engines, and finally the efficiency of them is calculated.

Analysis of the Temporal-Spatial Characteristics of Cloud Parameters and the Relationship with the Precipitation over Qilian Mountains Area in Northwest China

&lt;p&gt;Qilian mountains, located in the arid and semi-arid region of Northwest China, has more amount of natural precipitation than that on both north and south sides, with unique geographical environment and abundant water vapor supply. It is a very important water resource for the surrounding areas. To deeper understand the features of cloud over the areas is significant for the utilization of cloud water resources and sustainable development in this region. In this article, based on MOD08-M3 data, grid ground precipitation data and FY-2 series satellite cloud parameter inversion products, the spatial and temporal features of cloud macro/micro physical parameters, such as Cloud Amount&amp;#65288;CA&amp;#65289;, Cloud Water Path&amp;#65288;CWP&amp;#65289;, Cloud Top Temperature&amp;#65288;CTT&amp;#65289;, Cloud Top Pressure&amp;#65288;CTP&amp;#65289;, Cloud Optical Depth&amp;#65288;COD&amp;#65289; and Cloud Particle Effective Radius (CPER) over Qilian Mountains area were analyzed, as well as the relationship between the precipitation and cloud parameters. The results are as follows:&lt;/p&gt;&lt;ul&gt;&lt;li&gt;(1) The regional average values of CA, CWP, CTP, COD and CPER in Qilian Mountains area are 55.50 %, 148.95 g/m&amp;#178;, -21.13 &amp;#8451;, 456.56 hPa, 12.64 and 21.04 &amp;#956;m, respectively. From 2006 to 2015, CA, CWP, COD and CPER decreased by 2.3 %, 21 g/m&amp;#178;, 0.68 and 0.51 &amp;#956;m, respectively. CTT and CTP increased by 1.9 &amp;#8451; and 65.2 hPa, respectively. Cloud water resources over the area are abundant.&lt;/li&gt; &lt;li&gt;(2) There is the richest cloud water resource over the main area of Qilian Mountains, and the cloud parameter condition in Wushaoling area is the best for precipitation. The high value areas of CA in four seasons are distributed in Xining and surroundings, main and south part of mountain range, and Lenghu area, respectively. The high value areas of CWP in four seasons are located in the northeast, north-middle the main part of mountain area and the eastern side of Subei, respectively. The high value areas of COD are located in the east of Subei in winter and in the southeast of the study area in other seasons. The high value areas of CPER in spring are located in the region except Hexi Corridor. In other seasons they are located between Lenghu and Subei, Subei and Tuole, and in the northeast of range, respectively.&lt;/li&gt; &lt;li&gt;(3) The monthly precipitation is positively correlated with CA , CWP, COD, but negatively correlated with CTT and CTP. The relationship between CPERs and precipitation is positive in January, April, July, November and December, but negative in other months. CA and CPERs are most correlated with precipitation in May and September, respectively. while the correlation between other cloud parameters and precipitation are the highest in January.&lt;/li&gt; &lt;li&gt;(4) When the values of COD and CPER are too small or too large, the actual precipitation will be limited.&lt;/li&gt; &lt;/ul&gt;&lt;p&gt;&lt;strong&gt;Key words: &lt;/strong&gt;Cloud physical parameters; Precipitation; Water resource; Qilian Mountains&lt;/p&gt;

Observed HIRS and MODIS High-Cloud Frequencies in the 2000s

This paper compares the cloud parameter data records derived from High Resolution Infrared Radiation Sounder (HIRS) and Moderate Resolution Imaging Spectroradiometer (MODIS) measurements from the years 2003 through 2013. Cloud-top pressure (CTP) and effective emissivity (εf; cloud emissivity multiplied by cloud fraction) are derived using the 15-μm spectral bands in the CO2 absorption band and implementing the CO2-slicing technique; the approach is robust for high semitransparent clouds but weak for low clouds with little thermal contrast from clear-sky radiances. The high-cloud (HiCld; with CTP less than 440 hPa) seasonal cycles of HIRS and MODIS observations are found to be in sync, but the HIRS frequency of detection is about 10% higher than that of MODIS (which is attributed to a lower threshold for cloud detection in the HIRS CO2 bands). Differences are largest during nighttime and at the beginning of the time series (2003–06). Both show Northern Hemisphere (NH) and Southern Hemisphere (SH) seasonal HiClds are out of phase and both agree within 2% on NH–SH HiCld differences. During the summer, maximum HiCld frequency averages 5% more in the NH.

Precipitation Clouds Delineation Scheme in Tropical Cyclones and Its Validation Using Precipitation and Cloud Parameter Datasets from TRMM

Utilizing the cloud parameters derived from the Tropical Rainfall Measuring Mission (TRMM) Visible and Infrared Scanner and the near-surface rainfall detected by the TRMM Precipitation Radar, the differences of cloud parameters for precipitating clouds (PCs) and nonprecipitating clouds (NPCs) are examined in tropical cyclones (TCs) during daytime from June to September 1998–2010. A precipitation delineation scheme that is based on cloud parameter thresholds is proposed and validated using the independent TC datasets in 2011 and observational datasets from Terra/MODIS. Statistical analysis of these results shows that the differences in the effective radius of cloud particles Re are small for PCs and NPCs, while thick clouds with large cloud optical thickness (COT) and liquid water path (LWP) can be considered as candidates for PCs. The probability of precipitation increases rapidly as the LWP and COT increase, reaching ~90%, whereas the probability of precipitation reaches a peak value of only 30% as Re increases. The combined threshold of a brightness temperature at 10.8 μm (BT4) of 270 K and an LWP of 750 g m−2 shows the best performance for precipitation discrimination at the pixel levels, with the probability of detection (POD) reaching 68.2% and false-alarm ratio (FAR) reaching 31.54%. From MODIS observations, the composite scheme utilizing BT4 and LWP also proves to be a good index, with POD reaching 77.39% and FAR reaching 24.2%. The results from this study demonstrate a potential application of real-time precipitation monitoring in TCs utilizing cloud parameters from visible and infrared measurements on board geostationary weather satellites.

Multi-sensor measurements of mixed-phase clouds above Greenland

Liquid-only and mixed-phase clouds in the Arctic strongly affect the regional surface energy and ice mass budgets, yet much remains unknown about the nature of these clouds due to the lack of intensive measurements. Lidar measurements of these clouds are challenged by very large signal dynamic range, which makes even seemingly simple tasks, such as thermodynamic phase classification, difficult. This work focuses on a set of measurements made by the Clouds Aerosol Polarization and Backscatter Lidar at Summit, Greenland and its retrieval algorithms, which use both analog and photon counting as well as orthogonal and non-orthogonal polarization retrievals to extend dynamic range and improve overall measurement quality and quantity. Presented here is an algorithm for cloud parameter retrievals that leverages enhanced dynamic range retrievals to classify mixed-phase clouds. This best guess retrieval is compared to co-located instruments for validation.

Null and timelike geodesics of the Schwarzschild black hole with string cloud background

The trajectories of the time-like and null geodesics for radial and circular motion of the Schwarzschild black hole with string cloud background are investigated and compared with the Schwarzschild case without string clouds. It is found that in the presence of the string cloud parameter, the radius of the orbits is larger than the radius of the orbits in the case of the Schwarzschild black hole without string cloud parameter. Effective potential is calculated and it is observed that as the value of string cloud parameter increases the particle can more easily escape to infinity. Stability of the circular orbits is also discussed.