ROMA (Rank-Ordered Multifractal Analyses) of intermittency in space  plasmas – a brief tutorial review

Abstract. Intermittent fluctuations are the consequence of the dynamic interactions of multiple coherent or pseudo-coherent structures of varied sizes in the stochastic media (Chang, 1999). We briefly review here a recently developed technique, the Rank-Ordered Multifractal Analysis (ROMA), which is both physically explicable and quantitatively accurate in deciphering the multifractal characteristics of such intermittent structures (Chang and Wu, 2008). The utility of the method is demonstrated using results obtained from large-scale 2-D MHD simulations as well as in-situ observations of magnetic field fluctuations from the interplanetary and magnetospheric cusp regions, and the broadband electric field oscillations from the auroral zone.

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MESSENGER observations of planetary ion enhancements at Mercury’s northern magnetospheric cusp during Flux Transfer Event Showers

10.21203/rs.3.rs-1138782/v1 ◽

2021 ◽

Author(s):

Weijie Sun ◽

James Slavin ◽

Anna Milillo ◽

Ryan Dewey ◽

Stefano Orsini ◽

...

Keyword(s):

Solar Wind ◽

Large Scale ◽

Transfer Event ◽

Order Of Magnitude ◽

In Situ Observations ◽

Flux Transfer ◽

Magnetospheric Cusp ◽

Upward Moving ◽

Entry Layer

Abstract At Mercury, several processes can release ions and neutrals out of the planet’s surface. Here we present enhancements of dayside planetary ions in the solar wind entry layer during flux transfer event (FTE) “showers” near Mercury’s northern magnetospheric cusp. In this entry layer, solar wind ions are accelerated and move downward (i.e. planetward) toward the cusps, which sputter upward-moving planetary ions within 1 minute. The precipitation rate is enhanced by an order of magnitude during FTE showers and the neutral density of the exosphere can vary by >10% due to this FTE-driven sputtering. These in situ observations of enhanced planetary ions in the entry layer likely correspond to an escape channel of Mercury’s planetary ions, and the large-scale variations of the exosphere observed on minute-timescales by ground-based telescopes. Comprehensive, future multi-point measurements made by BepiColombo will greatly enhance our understanding of the processes contributing to Mercury’s dynamic exosphere and magnetosphere.

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What Is the Impact of Additional Tropical Observations on a Modern Data Assimilation System?

Monthly Weather Review ◽

10.1175/mwr-d-18-0120.1 ◽

2019 ◽

Vol 147 (7) ◽

pp. 2433-2449

Author(s):

Laura C. Slivinski ◽

Gilbert P. Compo ◽

Jeffrey S. Whitaker ◽

Prashant D. Sardeshmukh ◽

Jih-Wang A. Wang ◽

...

Keyword(s):

El Niño ◽

Large Scale ◽

El Nino ◽

Mean Square ◽

Observational Network ◽

In Situ Observations ◽

The Mean ◽

The Impact ◽

Assimilation System

Abstract Given the network of satellite and aircraft observations around the globe, do additional in situ observations impact analyses within a global forecast system? Despite the dense observational network at many levels in the tropical troposphere, assimilating additional sounding observations taken in the eastern tropical Pacific Ocean during the 2016 El Niño Rapid Response (ENRR) locally improves wind, temperature, and humidity 6-h forecasts using a modern assimilation system. Fields from a 50-km reanalysis that assimilates all available observations, including those taken during the ENRR, are compared with those from an otherwise-identical reanalysis that denies all ENRR observations. These observations reveal a bias in the 200-hPa divergence of the assimilating model during a strong El Niño. While the existing observational network partially corrects this bias, the ENRR observations provide a stronger mean correction in the analysis. Significant improvements in the mean-square fit of the first-guess fields to the assimilated ENRR observations demonstrate that they are valuable within the existing network. The effects of the ENRR observations are pronounced in levels of the troposphere that are sparsely observed, particularly 500–800 hPa. Assimilating ENRR observations has mixed effects on the mean-square difference with nearby non-ENRR observations. Using a similar system but with a higher-resolution forecast model yields comparable results to the lower-resolution system. These findings imply a limited improvement in large-scale forecast variability from additional in situ observations, but significant improvements in local 6-h forecasts.

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In situ observations of magnetic field fluctuations

Advances in Space Research ◽

10.1016/j.asr.2005.02.048 ◽

2005 ◽

Vol 35 (4) ◽

pp. 625-635 ◽

Cited By ~ 14

Author(s):

Géza Erdős ◽

André Balogh

Keyword(s):

Magnetic Field ◽

Field Fluctuations ◽

In Situ Observations

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Evaluating model-simulated and satellite-derived SM using in situ observations under different environment conditions in China

10.5194/egusphere-egu2020-2819 ◽

2020 ◽

Author(s):

Yuanyuan Wang ◽

Guicai Li

Keyword(s):

Land Surface ◽

Large Scale ◽

Microwave Remote Sensing ◽

Ground Truth ◽

Original Data ◽

Observation Data ◽

Monitoring Networks ◽

The Future ◽

In Situ Observations

Soil moisture (SM) is a key variable in understanding the climate system through its controls on the land surface energy and water budget. Large scale SM products have become increasingly available thanks to development in microwave remote sensing and land surface modeling. Comprehensive assessments on the reliability of satellite-derived and model-simulated SM products are essential for their improvement and application. In this research, the active, passive and combined Climate Change Initiative (CCI V04.2) SM products and the China Land Data Assimilation System (CLDAS V2.0) SM products were evaluated by comparing with in situ observed data over three networks in China: Hebi, Naqu and Heihe. The three sites have different environmental conditions and sensor densities, providing observations covering more than 2 years. Four statistic scores were calculated: R (considering both original data and anomalies), Bias, RMSE, ubRMSE. TC (Triple Collocation) analysis was also carried out in which uncertainties in observations are taken into account. Results indicate that the performance of the two SM products varies between the monitoring networks. For Naqu site, both products show good performance, with CCI-SM showing slightly higher R and lower ubRMSE. For Hebi site, CLDAS-SM performs better than CCI-SM, whereas for Heihe site, CLDAS-SM performs worse than CCI-SM. The expected uncertainty (0.04 m3/m3) can be achieved in Naqu and Heihe site by CCI-SM, and in Hebi and Naqu site by CLDAS-SM, which is quite encouraging. The two products agree in terms of sign of the Bias value, which is positive in Hebi and negative in Naqu and Heihe. Among all the three networks, Heihe site exhibits the lowest accuracy due to its complicated terrain and heterogeneous land surface. Ranom of CLDAS-SM in Heihe is close to 0, indicating its inability to capture short term variability. TC results reveal that for Naqu site the observation data have quite good qualities, while for Hebi site CLDAS-SM is more approximate to &#8216;ground truth&#8217; than in situ observations, suggesting a refinement of network maybe needed in the future. Overall, the two products are complementary. CLDAS-SM performs better in populated area (e.g., Hebi) where meteorological forcing is more accurate and CCI-SM performs better in remote areas (Naqu, Heihe) where RFI is usually low. More reliable validation networks are needed in the future to comprehensively understand the advantages and disadvantage of the two SM products in China.

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WETCHIMP-WSL: intercomparison of wetland methane emissions models over West Siberia

Biogeosciences Discussions ◽

10.5194/bgd-12-1907-2015 ◽

2015 ◽

Vol 12 (2) ◽

pp. 1907-1973 ◽

Cited By ~ 8

Author(s):

T. J. Bohn ◽

J. R. Melton ◽

A. Ito ◽

T. Kleinen ◽

R. Spahni ◽

...

Keyword(s):

Climate Change ◽

Large Scale ◽

Methane Emissions ◽

High Latitudes ◽

The West ◽

Wetland Area ◽

Forward Models ◽

Ch4 Emissions ◽

In Situ Observations

Abstract. Wetlands are the world's largest natural source of methane, a powerful greenhouse gas. The strong sensitivity of methane emissions to environmental factors such as soil temperature and moisture has led to concerns about potential positive feedbacks to climate change. This risk is particularly relevant at high latitudes, which have experienced pronounced warming and where thawing permafrost could potentially liberate large amounts of labile carbon over the next 100 years. However, global models disagree as to the magnitude and spatial distribution of emissions, due to uncertainties in wetland area and emissions per unit area and a scarcity of in situ observations. Recent intensive field campaigns across the West Siberian Lowland (WSL) make this an ideal region over which to assess the performance of large-scale process-based wetland models in a high-latitude environment. Here we present the results of a follow-up to the Wetland and Wetland CH4 Intercomparison of Models Project (WETCHIMP), focused on the West Siberian Lowland (WETCHIMP-WSL). We assessed 21 models and 5 inversions over this domain in terms of total CH4 emissions, simulated wetland areas, and CH4 fluxes per unit wetland area and compared these results to an intensive in situ CH4 flux dataset, several wetland maps, and two satellite inundation products. We found that: (a) despite the large scatter of individual estimates, 12 year mean estimates of annual total emissions over the WSL from forward models (5.34 ± 0.54 Tg CH4 y-1), inversions (6.06 ± 1.22 Tg CH4 y-1), and in situ observations (3.91 ± 1.29 Tg CH4 y-1) largely agreed, (b) forward models using inundation products alone to estimate wetland areas suffered from severe biases in CH4 emissions, (c) the interannual timeseries of models that lacked either soil thermal physics appropriate to the high latitudes or realistic emissions from unsaturated peatlands tended to be dominated by a single environmental driver (inundation or air temperature), unlike those of inversions and more sophisticated forward models, (d) differences in biogeochemical schemes across models had relatively smaller influence over performance; and (e) multi-year or multi-decade observational records are crucial for evaluating models' responses to long-term climate change.

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Magnetic reconnection driven by filament eruption in the 7 June 2011 event

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313011745 ◽

2013 ◽

Vol 8 (S300) ◽

pp. 502-503

Author(s):

L. van Driel-Gesztelyi ◽

D. Baker ◽

T. Török ◽

E. Pariat ◽

L. M. Green ◽

...

Keyword(s):

Magnetic Reconnection ◽

Large Scale ◽

Coronal Magnetic Field ◽

Filament Eruption ◽

Mhd Simulations ◽

Reconnection Region ◽

Solar Eruptions ◽

Magnetic Modelling ◽

First Time

AbstractDuring an unusually massive filament eruption on 7 June 2011, SDO/AIA imaged for the first time significant EUV emission around a magnetic reconnection region in the solar corona. The reconnection occurred between magnetic fields of the laterally expanding CME and a neighbouring active region. A pre-existing quasi-separatrix layer was activated in the process. This scenario is supported by data-constrained numerical simulations of the eruption. Observations show that dense cool filament plasma was re-directed and heated in situ, producing coronal-temperature emission around the reconnection region. These results provide the first direct observational evidence, supported by MHD simulations and magnetic modelling, that a large-scale re-configuration of the coronal magnetic field takes place during solar eruptions via the process of magnetic reconnection.

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The 25-Day-Period Large-Scale Oscillations in the Argentine Basin Revisited

Journal of Physical Oceanography ◽

10.1175/jpo2766.1 ◽

2005 ◽

Vol 35 (8) ◽

pp. 1473-1479 ◽

Cited By ~ 11

Author(s):

Chang-Kou Tai ◽

Lee-Lueng Fu

Keyword(s):

Simulation Study ◽

Large Scale ◽

Space Time ◽

Sea Surface ◽

Time Sampling ◽

Numerical Studies ◽

In Situ Observations ◽

Ocean Topography ◽

Argentine Basin

Abstract From sea surface height measurements made by the Ocean Topography Experiment (TOPEX)/Poseidon satellite, Fu et al. found and described large-scale oscillations at the period of 25 days in the Argentine Basin of the South Atlantic Ocean. These oscillations were previously hinted at by in situ observations. Only the extensive space–time sampling capability of TOPEX/Poseidon, however, was able to give a complete description of the phenomenon as a counterclockwise-rotating dipole centered at 45°S, 317°E over the Zapiola Rise. Fu et al. also undertook theoretical and numerical studies to suggest that the phenomenon is a resonantly excited barotropic normal mode of the locally closed f/H contour. In a simulation study, however, they also found that the space–time smoothing scheme employed would probably lower the amplitude of the estimated phenomenon by 30%–40%. By reprocessing the data using a different method and showing the amplitude to be almost 2 times as large, in this note it is confirmed that this is indeed the case. The original 5-yr study has also been extended to nearly 10 yr, demonstrating that the same phenomenon has persisted for almost 10 yr.

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From satellite altimetry to Argo and operational oceanography: three revolutions in oceanography

Ocean Science Discussions ◽

10.5194/osd-10-1127-2013 ◽

2013 ◽

Vol 10 (4) ◽

pp. 1127-1167 ◽

Cited By ~ 3

Author(s):

P. Y. Le Traon

Keyword(s):

High Resolution ◽

Real Time ◽

Sea Level ◽

Ocean Circulation ◽

Satellite Altimetry ◽

Large Scale ◽

Global Ocean ◽

Operational Oceanography ◽

In Situ Observations

Abstract. The launch of the US/French mission Topex/Poseidon (T/P) (CNES/NASA) in August 1992 was the start of a revolution in oceanography. For the first time, a very precise altimeter system optimized for large scale sea level and ocean circulation observations was flying. T/P alone could not observe the mesoscale circulation. In the 1990s, the ESA satellites ERS-1/2 were flying simultaneously with T/P. Together with my CLS colleagues, we demonstrated that we could use T/P as a reference mission for ERS-1/2 and bring the ERS-1/2 data to an accuracy level comparable to T/P. Near real time high resolution global sea level anomaly maps were then derived. These maps have been operationally produced as part of the SSALTO/DUACS system for the last 15 yr. They are now widely used by the oceanographic community and have contributed to a much better understanding and recognition of the role and importance of mesoscale dynamics. Altimetry needs to be complemented with global in situ observations. In the end of the 90s, a major international initiative was launched to develop Argo, the global array of profiling floats. This has been an outstanding success. Argo floats now provide the most important in situ observations to monitor and understand the role of the ocean on the earth climate and for operational oceanography. This is a second revolution in oceanography. The unique capability of satellite altimetry to observe the global ocean in near real time at high resolution and the development of Argo were essential to the development of global operational oceanography, the third revolution in oceanography. The Global Ocean Data Assimilation Experiment (GODAE) was instrumental in the development of the required capabilities. This paper provides an historical perspective on the development of these three revolutions in oceanography which are very much interlinked. This is not an exhaustive review and I will mainly focus on the contributions we made together with many colleagues and friends.

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Reconstruction of the Parker spiral with the Reverse In situ data and MHD APproach - RIMAP

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2020072 ◽

2020 ◽

Author(s):

Ruggero Biondo ◽

Alessandro Bemporad ◽

Andrea Mignone ◽

Fabio Reale

Keyword(s):

Interplanetary Medium ◽

Small Scale ◽

Reconstruction Technique ◽

The Sun ◽

Plasma Parameters ◽

In Situ Data ◽

Mhd Simulations ◽

Solar Eruptions ◽

In Situ Observations

The reconstruction of plasma parameters in the interplanetary medium is very important to understand the interplanetary propagation of solar eruptions and for Space Weather application purposes. Because only a few spacecraft are measuring in situ these parameters, reconstructions are currently performed by running complex numerical Magneto-hydrodynamic (MHD) simulations starting from remote sensing observations of the Sun. Current models apply full 3D MHD simulations of the corona or extrapolations of photospheric magnetic fields combined with and semiempirical relationships to derive the plasma parameters on a sphere centered on the Sun (inner boundary). The plasma is then propagated in the interplanetary medium up to the Earth’s orbit and beyond. Nevertheless, this approach requires significant theoretical and computational efforts, and the results are only in partial agreement with the in situ observations. In this paper we describe a new approach to this problem called RIMAP - Reverse In situ data and MHD APproach. The plasma parameters in the inner boundary at 0.1 AU are derived directly from the in situ measurements acquired at 1 AU, by applying a back reconstruction technique to remap them into the inner heliosphere. This remapping is done by using the Weber and Davies solar wind theoretical model to reconstruct the wind flowlines. The plasma is then re-propagated outward from 0.1 AU by running a MHD numerical simulation based on the PLUTO code. The interplanetary spiral reconstructions obtained with RIMAP are not only in a much better agreement with the in situ observations, but are also including many more small-scale longitudinal features in the plasma parameters that are not reproduced with the approaches developed so far.

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On the structure of the extra-tropical transition layer from in-situ observations

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-28033-2012 ◽

2012 ◽

Vol 12 (10) ◽

pp. 28033-28068

Author(s):

I. Pisso ◽

K. S. Law ◽

F. Fierli ◽

P. H. Haynes ◽

P. Hoor ◽

...

Keyword(s):

Transition Layer ◽

Large Scale ◽

Trace Gases ◽

Potential Temperature ◽

Local Maximum ◽

Upper Limit ◽

Relative Coordinates ◽

In Situ Observations ◽

Definition Of

Abstract. In-situ observations of atmospheric tracers from multiple measurement campaigns over the period 1994–2007 were combined to investigate the Extra-tropical Transition Layer (ExTL) region and the properties of large scale meridional transport. We used potential temperature, equivalent latitude and distance relative to the local dynamical tropopause as vertical coordinates to highlight the behaviour of trace gases in the tropopause region. Vertical coordinates based on constant PV surfaces allowed us to relate the dynamical definition of the tropopause with trace gases distributions and vertical gradients and hence analyse its latitudinal dependence and seasonal variability. Analysis of the available data provides a working definition of the upper limit of the ExTL based on the upper limit of the region of high vertical CO gradient in PV relative coordinates. A secondary local maximum in vertical O3 gradient can be used a proxy for the lower limit, although it is less clearly defined than that of CO. The sloping isopleths of CO and O3 mixing ratios and the CO mixing ratio gradient are consistent with isopleths in purely dynamical diagnostics such as χ30 d, the proportion of air masses in contact with the PBL within one month and underline the differences between the PV based and chemical tropopauses. The use of tropopause relative coordinates allows different seasons to be analysed together to produce climatological means. The weak dependence of dynamical diagnostics of transport on the absolute values of tracer concentrations makes them a suitable process-oriented tool to evaluate global chemical models and make Lagrangian comparisons.

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