The seasonal cycle of planetary boundary layer depth determined using COSMIC radio occultation data

Chan, Ka Man; Wood, Robert

doi:10.1002/2013jd020147

Cited by 87 publications

(87 citation statements)

References 43 publications

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“…Across all years, h was found to occur between 1.1 and 1.8 km with a median of 1.5 km above Alaska, consistent with estimates derived from satellite retrievals (Chan and Wood, 2013). On average, h in May-September was 30 % higher than in April, October, or November.…”

Section: Mixed Layersupporting

confidence: 83%

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Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

Hartery¹,

Commane

Lindaas

et al. 2018

Atmos. Chem. Phys.

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Abstract. Methane (CH 4 ) is the second most important greenhouse gas but its emissions from northern regions are still poorly constrained. In this study, we analyze a subset of in situ CH 4 aircraft observations made over Alaska during the growing seasons of 2012-2014 as part of the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE). Net surface CH 4 fluxes are estimated using a Lagrangian particle dispersion model which quantitatively links surface emissions from Alaska and the western Yukon with observations of enhanced CH 4 in the mixed layer. We estimate that between May and September, net CH 4 emissions from the region of interest were 2.2 ± 0.5 Tg, 1.9 ± 0.4 Tg, and 2.3 ± 0.6 Tg of CH 4 for 2012, 2013, and 2014, respectively. If emissions are only attributed to two biogenic eco-regions within our domain, then tundra regions were the predominant source, accounting for over half of the overall budget despite only representing 18 % of the total surface area. Boreal regions, which cover a large part of the study region, accounted for the remainder of the emissions. Simple multiple linear regression analysis revealed that, overall, CH 4 fluxes were largely driven by soil temperature and elevation. In regions specifically dominated by wetlands, soil temperature and moisture at 10 cm depth were important explanatory variables while in regions that were not wetlands, soil temperature and moisture at 40 cm depth were more important, suggesting deeper methanogenesis in drier soils. Although similar environmental drivers have been found in the past to control CH 4 emissions at local scales, this study shows that they can be used to generate a statistical model to estimate the regional-scale net CH 4 budget.

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Section: Mixed Layersupporting

confidence: 83%

“…We estimate the bottom of the free troposphere (h) by calculating the refractivity (N) using parameters measured at different altitudes on the aircraft (Chan and Wood, 2013;Bean and Dutton, 1966):…”

Section: Mixed Layermentioning

confidence: 99%

Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

Hartery¹,

Commane

Lindaas

et al. 2018

Atmos. Chem. Phys.

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“…At the top of the CBL, the refractivity sharply decreases forming minima in N , which is generally used to identify the CBL height especially using GPS radio occultation data, and it is preferred over the use of θ and q (Basha and Ratnam, 2009). However, it should be noted that the multiple local minima can be seen in N and the one that is at a minimum most below 3.5 km is identified as the CBL (Chan and Wood, 2013). Fixing the height criterion of 3.5 km as the upper limit is generally done to avoid mid-level inversions, if any.…”

Section: Evolution Of the Cbl In Clear-sky Conditionsmentioning

confidence: 99%

“…The CBL and the lifting condensa- Garratt, 1992;Medeiros et al, 2005). The ABL has strong seasonal characteristics; however, it changes even within the season (Seidel et al, 2010;Bianco et al, 2011;Chan and Wood, 2013;Guo et al, 2016) and is mainly related to thermodynamic conditions of the atmosphere. Hence, understanding of the day-to-day weather conditions and their influence on the ABL variability is essential for air quality assessment and numerical weather simulations.…”

mentioning

confidence: 99%

Thermodynamic structure of the convective boundary layer (CBL) over the Indian monsoon region during CAIPEEX campaigns

et al. 2017

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Abstract. Spatial and temporal variability in the convective boundary layer (CBL) height for the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) study period are examined using the data collected from high-resolution radiosondes during May-September 2009 over the Indian monsoon region. In total, 57 radiosonde launchings were carried out at ∼ 11:00-17:00 IST over six different stations covering a large geographical region, ranging from latitude ∼ 13 to 32 • N and longitude 73 to 92 • E. Of the total 57 launchings, 17 were made during cloudy conditions during which relative humidity (RH) was found to be greater than 83 % for an ∼ 1.0 km layer at various altitudes below 6 km. Within the layer the difference between saturated equivalent potential temperature and equivalent potential temperature is small, and it satisfies the condition that RH > 83 % for about 1 km is considered as the cloudy layer. There are eight cases when the cloud-topped boundary layer (CTBL) and 19 cases when fair-weather boundary layer (FWBL) is observed. The CBL heights are obtained using thermodynamic profiles, which vary from ∼ 0.4 to 2.5 km a.g.l. The formation of the cloud layers above the boundary layer generally lowers the CBL height and is responsible for its day-to-day variability. The development of the cloud beneath the boundary layer generally elevates the CBL, which is also responsible for the large day-to-day variability in the CBL. The FWBL identified using relative invariance of the thermodynamic profiles varies from ∼ 2.0 to 5.5 km, which is clearly marked by a local minimum in the refractivity gradient. During cloudy days, the CBL is found to be shallow and the surface temperature lower when compared to clear-sky days. The CBL and the lifting condensation level (LCL) heights are randomly related and are found to be at a lower height during cloudy days when compared to clear-sky days. Finally, the typical comparison between the CBL height obtained using thermodynamic profiles and backscattering profiles using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) is examined.

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“…Additionally, the L-band GNSS RO signals can penetrate through clouds and precipitation (Solheim et al, 1999), which are common at the height at the top of the PBL. These features make GNSS RO a valuable tool for sensing the PBL (Guo et al, 2011;Ao et al, 2012;Xie et al, 2012;Chan and Wood, 2013;Ho et al, 2015).…”

mentioning

confidence: 99%

Correcting negatively biased refractivity below ducts in GNSS radio occultation: an optimal estimation approach towards improving planetary boundary layer (PBL) characterization

Wang

Juárez

et al. 2017

Atmos. Meas. Tech.

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Abstract. Global Navigation Satellite System (GNSS) radio occultation (RO) measurements are promising in sensing the vertical structure of the Earth's planetary boundary layer (PBL). However, large refractivity changes near the top of PBL can cause ducting and lead to a negative bias in the retrieved refractivity within the PBL (below ∼ 2 km). To remove the bias, a reconstruction method with assumption of linear structure inside the ducting layer models has been proposed by Xie et al. (2006). While the negative bias can be reduced drastically as demonstrated in the simulation, the lack of high-quality surface refractivity constraint makes its application to real RO data difficult. In this paper, we use the widely available precipitable water (PW) satellite observation as the external constraint for the bias correction. A new framework is proposed to incorporate optimization into the RO reconstruction retrievals in the presence of ducting conditions. The new method uses optimal estimation to select the best refractivity solution whose PW and PBL height best match the externally retrieved PW and the known a priori states, respectively. The near-coincident PW retrievals from AMSR-E microwave radiometer instruments are used as an external observational constraint. This new reconstruction method is tested on both the simulated GNSS-RO profiles and the actual GNSS-RO data. Our results show that the proposed method can greatly reduce the negative refractivity bias when compared to the traditional Abel inversion.

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The seasonal cycle of planetary boundary layer depth determined using COSMIC radio occultation data

Cited by 87 publications

References 43 publications

Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

Thermodynamic structure of the convective boundary layer (CBL) over the Indian monsoon region during CAIPEEX campaigns

Correcting negatively biased refractivity below ducts in GNSS radio occultation: an optimal estimation approach towards improving planetary boundary layer (PBL) characterization

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