Influence of Doubled CO2 on Ozone via Changes in the Brewer–Dobson Circulation

In this short note, the effect of enhanced circulation due to doubling CO2 on ozone is investigated. The difference of Brewer–Dobson circulation (BDC) between the doubled CO2 and control run from an idealized atmospheric general circulation model is added to the BDC climatology derived from National Centers for Environmental Prediction—Department of Energy Reanalysis 2 (NCEP2) from 1979 to 2002. Then it is used to drive the California Institute of Technology/Jet Propulsion Laboratory (Caltech/JPL) two-dimensional chemistry and transport model. The results reveal that the total ozone increases by 7 and 3.5 Dobson units (DU) in the high latitudes of the Northern and Southern Hemispheres, respectively, and decreases by 4 DU in the Tropics as a result of the increase in BDC associated with doubled CO2. If the change of eddy mixing coefficients after doubling CO2 is also considered, the total ozone will increase by 6.5 and 3 DU in the high latitudes of the Northern and Southern Hemispheres after combining both effects from the change in BDC and eddy mixing coefficients

A compact 6-bit phase shifter with high-power capacity based on composite right/left-handed transmission line

The EuMC 2010 Conference was one of the 4 conferences held during the 13th European Microwave Week (EuMW2010): "Connecting the World", Paris, France, 26 September-1 October 2010A compact 6-bit phase shifter with high power-handling capacity is designed based on the use of metamaterial, composite right/left-handed transmission line (CRLH-TL). Eight PIN diodes mounted on the fingers of the CRLH-TL are used as switches to control the phase incursion of the input signal. Different phase shifts are achieved by using different states of the switches (PIN diodes) determined by 6 controlling bits. Since the surface current flowing through each of the switches is only a fraction of the total current through the device, the power handled by each of the PIN diodes is much smaller than the total power through the device; thus the power-handling capacity of the phase shifter can be greatly improved. The phase shifter is designed to provide a phase-shift range from 0° to 360° at a step of 5.625° and operate in the frequency band from 9.2 to 9.8 GHz. Simulation results and measurement results of the prototype agree closely and show that the phase shifter has a much higher power-handling capacity than that of the PIN diode and low insertion losses across the operating frequency band. © 2010 EuMA.published_or_final_versionThe 40th European Microwave Conference (EuMC 2010), Pairs, France, 28-30 September 2010. In Proceedings of EuMC 2010, 2010, p. 437-44

A compact and UWB time-delay line inspired by CRLH TL unit cell

This paper presents the design of compact and ultra-wideband (UWB) time-delay lines inspired by the use of composite right/left-handed transmission line (CRLH TL) unit cell. A conventional CRLH TL unit cell is used as the basic elements for the design of time-delay lines and a rotated version of the unit cell is used to achieve ultrawide bandwidth operation. Time-delay lines for large time delays are designed by cascading the proposed unit cells, optimized using computer simulation and then fabricated on PCBs. A compact UWB time-delay line is designed by bending the time-delay line in a meander. For comparison, the time-delay line using the right-handed transmission line (RH TL) is also fabricated. Simulation and measurement results show that our proposed time-delay lines have ultrawide bandwidth operation and much longer time delays than that of the time-delay line based on RH TL. They also have the advantages of high return losses and low insertion losses. © 2010 IEEE.published_or_final_versionThe 2010 IEEE Region 10 International Conference (TENCON 2010), Fukuoka, Japan, 21-24 November 2010. In TENCON (IEEE Region 10 Conference) Proceedings, 2010, p. 868-87

A rectangular-shaped time-delay line inspired by CRLH TL unit cell for UWB operation

This paper presents the design of a rectangular-shaped ultra-wideband (UWB) time-delay line inspired by the use of composite right/left-handed transmission line (CRLH TL) unit cells. A rotated version of a conventional CRLH TL unit cell is used as the basic elements to achieve UWB operation. For comparison, time-delay lines using the right-handed transmission line (RH TL) and CRLH TL unit cells are also studied, fabricated and tested. Simulation and measurement results show that our proposed time-delay lines have high return loss, low insertion loss, UWB operation and much longer time delays than that of the time-delay line based on RH TL. © 2010 IEEE.published_or_final_versionThe 12th IEEE International Conference on Communication Systems (ICCS 2010), Singapore, 17-19 November 2010. In Proceedings of 12th ICCS, 2010, p. 27-3

Observed Tightening of Tropical Ascent in Recent Decades and Linkage to Regional Precipitation Changes

Climate models predict that the tropical ascending region should tighten under global warming, but observational quantification of the tightening rate is limited. Here we show that the observed spatial extent of the relatively moist, rainy and cloudy regions in the tropics associated with large‐scale ascent has been decreasing at a rate of −1%/decade (−5%/K) from 1979 to 2016, resulting from combined effects of interdecadal variability and anthropogenic forcings, with the former contributing more than the latter. The tightening of tropical ascent is associated with an increase in the occurrence frequency of extremely strong ascent, leading to an increase in the average precipitation rate in the top 1% of monthly rainfall in the tropics. At the margins of the convective zones such as the Southeast Amazonia region, the contraction of large‐scale ascent is related to a long‐term drying trend about −3.2%/decade in the past 38 years

A Multiple Scattering Polarized Radiative Transfer Model: Application to HD 189733b

We present a multiple scattering vector radiative transfer model which produces disk integrated, full phase polarized light curves for reflected light from an exoplanetary atmosphere. We validate our model against results from published analytical and computational models and discuss a small number of cases relevant to the existing and possible near-future observations of the exoplanet HD 189733b. HD 189733b is arguably the most well observed exoplanet to date and the only exoplanet to be observed in polarized light, yet it is debated if the planet's atmosphere is cloudy or clear. We model reflected light from clear atmospheres with Rayleigh scattering, and cloudy or hazy atmospheres with Mie and fractal aggregate particles. We show that clear and cloudy atmospheres have large differences in polarized light as compared to simple flux measurements, though existing observations are insufficient to make this distinction. Futhermore, we show that atmospheres that are spatially inhomogeneous, such as being partially covered by clouds or hazes, exhibit larger contrasts in polarized light when compared to clear atmospheres. This effect can potentially be used to identify patchy clouds in exoplanets. Given a set of full phase polarimetric measurements, this model can constrain the geometric albedo, properties of scattering particles in the atmosphere and the longitude of the ascending node of the orbit. The model is used to interpret new polarimetric observations of HD 189733b in a companion paper.Comment: 13 pages, 13 figures. Accepted for publication in Ap

Ultra-wideband time-delay line inspired by composite right/left-handed transmission line unit cell

Proceedings of the IEEE International Conference on Ultra-Wideband, 2010, v. 2, p. 607-610This paper presents a design of ultra-wideband time-delay line inspired by the composite right/left-handed transmission line (CRLH TL) unit cell. A rotated version of the conventional CRLH TL unit cell is used to increase the operating bandwidth. The time-delay line is optimized using computer simulation and then fabricated on a PCB for measurement. For comparison, the time-delay lines using the right-handed transmission line (RH TL) and periodic microstrip line (PML) are also designed, optimized and fabricated. Simulation and measurement results show that, for the same length of 60 mm, our proposed time-delay line has a much longer time delay of 2000 ps with high return loss and low insertion loss. © 2010 IEEE.published_or_final_versio

Designs of True-Time-Delay Lines and Phase Shifters Based on CRLH TL Unit Cells

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CPW-coupled-fed elliptical monopole UWB antenna with dual-band notched characteristic

This paper presents the results of a coplanar-waveguide (CPW)-coupled-fed elliptical monopole UWB antenna (CCFEMUA) with a dual band-notched characteristic. The antenna has a large bandwidth covering the frequency band from 2.4 GHz to 152 GHz with the return loss larger than 10 dB. Two band notches at 3.7GHZ and 4.8 GHz are realized by cutting two half-elliptical-arc slots on the radiation patch The return loss, radiation pattern, peak gain and efficiency of the antenna are studied using computer simulation.published_or_final_versio

Vertical Moist Thermodynamic Structure and Spatial–Temporal Evolution of the MJO in AIRS Observations

The atmospheric moisture and temperature profiles from the Atmospheric Infrared Sounder (AIRS)/Advanced Microwave Sounding Unit on the NASA Aqua mission, in combination with the precipitation from the Tropical Rainfall Measuring Mission (TRMM), are employed to study the vertical moist thermodynamic structure and spatial–temporal evolution of the Madden–Julian oscillation (MJO). The AIRS data indicate that, in the Indian Ocean and western Pacific, the temperature anomaly exhibits a trimodal vertical structure: a warm (cold) anomaly in the free troposphere (800–250 hPa) and a cold (warm) anomaly near the tropopause (above 250 hPa) and in the lower troposphere (below 800 hPa) associated with enhanced (suppressed) convection. The AIRS moisture anomaly also shows markedly different vertical structures as a function of longitude and the strength of convection anomaly. Most significantly, the AIRS data demonstrate that, over the Indian Ocean and western Pacific, the enhanced (suppressed) convection is generally preceded in both time and space by a low-level warm and moist (cold and dry) anomaly and followed by a low-level cold and dry (warm and moist) anomaly. The MJO vertical moist thermodynamic structure from the AIRS data is in general agreement, particularly in the free troposphere, with previous studies based on global reanalysis and limited radiosonde data. However, major differences in the lower-troposphere moisture and temperature structure between the AIRS observations and the NCEP reanalysis are found over the Indian and Pacific Oceans, where there are very few conventional data to constrain the reanalysis. Specifically, the anomalous lower-troposphere temperature structure is much less well defined in NCEP than in AIRS for the western Pacific, and even has the opposite sign anomalies compared to AIRS relative to the wet/dry phase of the MJO in the Indian Ocean. Moreover, there are well-defined eastward-tilting variations of moisture with height in AIRS over the central and eastern Pacific that are less well defined, and in some cases absent, in NCEP. In addition, the correlation between MJO-related midtropospheric water vapor anomalies and TRMM precipitation anomalies is considerably more robust in AIRS than in NCEP, especially over the Indian Ocean. Overall, the AIRS results are quite consistent with those predicted by the frictional Kelvin–Rossby wave/conditional instability of the second kind (CISK) theory for the MJO