Using a semi-analytical model to retrieve Secchi depth in coastal and estuarine waters

Liu, Xianfu; Meng, Xuejiao; Wang, Xiaoyong; Bi, Dayong; Chen, Lei; Lou, Quansheng

doi:10.1007/s13131-020-1620-2

Cited by 6 publications

(5 citation statements)

References 50 publications

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“…The Lee et al (2015) Z SD model has been applied in a number of regions (Shang et al 2016; Liu et al 2020 a , b ; Kahru et al 2022; Brewin et al 2023). We validated the satellite‐derived Z SD datasets at daily and 4.5‐km resolutions.…”

Section: Resultsmentioning

confidence: 99%

Multidecadal changes in ocean transparency: Decrease in a coastal upwelling region and increase offshore

Kahru

Lee

Ohman

2023

Limnology & Oceanography

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Detection of the effects of climate change on ocean ecosystems is often limited by the short duration of available time series. Here, we use ocean transparency measurements (the Secchi disk depth, ZSD) in the California Current Ecosystem since 1949 and combine them with satellite estimates. Historic in situ measurements of ZSD were irregular in space and time and are difficult to interpret in time series due to biases introduced by changing locations and timing. We normalize historic ZSD measurements with satellite‐derived mean climatology and create a merged in situ—satellite time series of ZSD for the last ~ 73 yr. Although interannual variability in ZSD is dominated by El Niño Southern Oscillation‐related variability (~ 50% of the total variance in many areas), a secular trend of decreasing transparency that is correlated with increasing productivity is detected 0–300 km from the coast in an area affected by coastal upwelling north of 27°N. In contrast, increasing transparency (correlated with decreasing productivity) is detected offshore (> 1000 km from the coast). In addition to those general trends, transparency is also increasing in coastal area off Baja California south of 27°N.

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Section: Resultsmentioning

confidence: 99%

Multidecadal changes in ocean transparency: Decrease in a coastal upwelling region and increase offshore

Kahru

Lee

Ohman

2023

Limnology & Oceanography

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“…The Sen trend method (Sen, 1968) and Mann-Kendall (MK) significant test were used to analyze the NDVI trend for 1986-2019. The Sen trend method can effectively avoids the influence of time-series data loss and data distribution form, and eliminates the interference of timeseries outliers (Liu et al, 2010), and the MK significant test (Man, 1945;kendall, 1975) was conducted to test the significance of the calculated Sen trend. The MK mutation test (Karpouzos et al, 2010) were conducted to determine the mutated NDVI change period and divide the dynamic process of NDVI change.…”

Section: Methodsmentioning

confidence: 99%

Dynamics of vegetation cover and its driving factors in the Qinling-Daba Mountains on regional scale for 1986-2019

Yao

Wang

2023

Preprint

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The Qinling-Daba Mountains is the transitional zone of the north and south of China. The vegetation in this area, characterized by complexity, heterogeneity and transition, is particularly sensitive to global climate change and human activities. Based on the normalized vegetation index (NDVI) data of the growing season from 1986 to 2019, which was synthesized by Landsat series satellite data on Google Earth Engine, this paper uses the methods of spatial analysis and Geo-detectors to clarify dynamics of vegetation cover and its main driving factors in the Qinling-Daba Mountains. The results show that: (1) vegetation coverage in study area shows a U-shaped NDVI distribution pattern in latitude, anti-U-shaped patterns in longitude and with altitude ascending. (2) the dynamics of vegetation coverage can be divided into two periods according to the result of MK mutation test (the breakthrough increasing period around 2005) and the trend of NDVI change: the slow increasing period with an increasing rate of 0.25%/a from 1986 to 2004 (R2 0.74), and the rapid increasing period with an increasing rate of 0.30%/a from 2005 to 2019 (R2 0.92). (3) Soil type, landform, vegetation type, land use type and annual average temperature are the main driving factors of vegetation dynamics in the Qinling-Daba Mountains, while annual precipitation, population density and GDP are the secondary driving factors of vegetation dynamics. The land use type and land management policies in the Qinling-Daba Mountains have a strong impact on vegetation cover change, and the climate warming in recent decades plays more important role than precipitation on the vegetation dynamics. These results are of great significance to comprehensively understand the impact of global climate warming and human activities on the natural environment of the Qinling-Daba Mountains.

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“…The Lee et al (2015) Z Sd model has been applied in a number of regions (e.g. Shang et al 2016, Liu et al 2020a. We did not attempt a rigorous verification with high-resolution satellite match-ups within a short period (e.g.…”

Section: Validation Of Satellite Estimatesmentioning

confidence: 99%

Baltic Sea transparency from ships and satellites: centennial trends

Kahru

Elmgren

Fleming³

et al. 2022

Mar. Ecol. Prog. Ser.

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Water transparency can be measured with optical instruments and estimated with satellite sensors, but such measurements have been widely available for only a few decades. Estimates of water transparency using a white disk called a Secchi disk have been made for over a century and can be used to estimate long-term trends. However, historic in situ measurements of the Secchi depth (ZSd) were irregular in space and time and are difficult to interpret in regular time series due to biases introduced by changing locations and the timing of measurements. Satellite data time series, on the other hand, have consistent resolution in both space and time but cover too short a time to resolve climate-scale trends. We normalized historic ZSd measurements in the Baltic Sea with a satellite-derived mean climatology at 5 d temporal and 4 km spatial resolutions and created a merged time series of ZSd for the last century. The mean ZSd in the Baltic Sea from 1927-2020 decreased by 4.2 ± 0.6 m at a rate of 0.045 ± 0.06 m yr-1. Most of the change happened before 1987, and a further decrease was evident primarily in the satellite data during the 1998-2008 period. After 2008, no significant trend in ZSd and or the coefficient of diffuse light attenuation was detected in the Baltic Sea. However, in some sub-basins of the Baltic Sea, the decrease in ZSd continued even after that. The decrease in spectral water transparency in recent decades was highest in the 412 nm band, indicating an increase in the concentration of chromophoric dissolved organic matter.

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Using a semi-analytical model to retrieve Secchi depth in coastal and estuarine waters

Cited by 6 publications

References 50 publications

Multidecadal changes in ocean transparency: Decrease in a coastal upwelling region and increase offshore

Multidecadal changes in ocean transparency: Decrease in a coastal upwelling region and increase offshore

Dynamics of vegetation cover and its driving factors in the Qinling-Daba Mountains on regional scale for 1986-2019

Baltic Sea transparency from ships and satellites: centennial trends

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