阅读说明：本技术 一种现场紫外荧光传感器的cdom处理方法 (CDOM processing method of on-site ultraviolet fluorescence sensor ) 是由 赵玮宁 宋贵生 聂红涛 于 2021-07-16 设计创作，主要内容包括：本发明涉及一种现场紫外荧光传感器的CDOM处理方法,包括下列步骤：数据获取：将紫外荧光传感器搭载在温盐深仪CTD上,设置CTD的输出变量,把CTD放入水域中进行测试；数据转换；数据质量控制：包括：CDOM测量值可能突然出现异常高值,需要在处理数据时进行去尖峰；数据平均：CTD上的深度数据与CDOM数据是一一对应的,根据分析的需要,将一定深度范围的CDOM数据进行滑动平均。(The invention relates to a CDOM processing method of an on-site ultraviolet fluorescence sensor, which comprises the following steps: data acquisition: carrying an ultraviolet fluorescence sensor on a thermohaline depth meter (CTD), setting an output variable of the CTD, and putting the CTD into a water area for testing; data conversion; and (3) data quality control: the method comprises the following steps: CDOM measurements can suddenly appear abnormally high, requiring de-spiking while processing data; data averaging: the depth data on the CTD is in one-to-one correspondence with the CDOM data, and the CDOM data in a certain depth range is subjected to moving average according to the analysis requirement.)

1. A CDOM processing method of an in-situ ultraviolet fluorescence sensor comprises the following steps:

1) data acquisition: carrying an ultraviolet fluorescence sensor on a thermohaline depth meter (CTD), setting an output variable of the CTD, and putting the CTD into a water area for testing;

2) data conversion: converting depth, temperature and salinity measured by an instrument and CDOM (compact disc read only memory) original data into a format which can be processed by Matlab;

3) and (3) data quality control: the method comprises the following steps:

errors due to sampling frequency may result in CDOM measurements that may have a 0 value, which needs to be reassigned to nan when processing data;

the CDOM measurement value may have a negative value, and the negative value needs to be reassigned to 0 when processing data;

during observation, the CDOM measurement may suddenly show abnormally high value, and needs to be de-peaked when processing data, as follows: the peak is determined based on the multiple of the standard deviation, the local standard deviation of the first derivative and the derivative of the CDOM profile at the corresponding time is calculated, if the ratio of the two exceeds a certain set threshold, the peak is determined to exist, and then the average value of the CDOM at the two ends of the peak is used for substitution.

4) Data averaging: the depth data on the CTD is in one-to-one correspondence with the CDOM data, and the CDOM data in a certain depth range is subjected to moving average according to the analysis requirement.

2. A CDOM processing method according to claim 1, wherein the step 4) is as follows: firstly, processing the depth data of the CTD into delta m average data to obtain the starting time corresponding to each delta m; secondly, according to the starting time, finding the CDOM time sequence of the corresponding time period, and averaging the CDOM time sequence to obtain delta m average CDOM section data.

Technical Field

The invention belongs to the field of marine science, and particularly relates to a CDOM data processing method measured by an Ultraviolet fluorescence sensor (SUVF for short) carried on a Sea-Bird 911plus warm salt Depth instrument (CTD).

Background

Dissolved Organic Matter (DOM) is a complex mixture of ingredients whose source and migration transformation processes affect the storage and transport of carbon in water and plays an important role in the biogeochemical modules of the global carbon cycle. The components of the DOM that absorb in the uv and visible spectrum are called Chromophoric DOM (CDOM), and the materials that absorb and emit fluorescence are called Fluorogenic DOM (FDOM). CDOM is ubiquitous in marine environments, affecting the optical properties of the water column, and can be used to track DOM biogeochemical cycling processes. SUVF is a high-performance low-power consumption fluorescent substance field measurement sensor, the measuring range includes CDOM, crude oil and ultraviolet fluorescent dye, its small, the energy consumption is low, the degree of sensitivity is high, the dynamic range is wide, can be in 6000 meters deep operation, operate this sensor under various conditions and do not use the chemical reagent, can provide accurate, real-time and continuous CDOM fluorescence data, it is the researcher to carry on the biochemical research of ocean, the crude oil detection, the helping hand in aspects such as water quality testing.

Disclosure of Invention

The invention provides a CDOM processing method of an in-situ ultraviolet fluorescence sensor. The method is mainly used for processing the original data with large quantity and singular values into the data with average and smooth depth range. And analyzing the processed data to know the space-time distribution characteristics of the CDOM in the ocean. The technical scheme adopted by the invention is as follows:

a CDOM processing method of an in-situ ultraviolet fluorescence sensor comprises the following steps:

1) data acquisition: carrying an ultraviolet fluorescence sensor on a thermohaline depth meter (CTD), setting an output variable of the CTD, and placing the CTD into a water area for testing;

2) data conversion: converting depth, temperature and salinity measured by an instrument and CDOM (compact disc read only memory) original data into a format which can be processed by Matlab;

3) and (3) data quality control: the method comprises the following steps:

errors due to sampling frequency may result in CDOM measurements that may have a 0 value, which needs to be reassigned to nan when processing data;

the CDOM measurement value may have a negative value, and the negative value needs to be reassigned to 0 when processing data;

during observation, the CDOM measurement may suddenly show abnormally high value, and needs to be de-peaked when processing data, as follows: the peak is determined based on the multiple of the standard deviation, the local standard deviation of the first derivative and the derivative of the CDOM profile at the corresponding time is calculated, if the ratio of the two exceeds a certain set threshold, the peak is determined to exist, and then the average value of the CDOM at the two ends of the peak is used for substitution.

4) Data averaging: the depth data on the CTD is in one-to-one correspondence with the CDOM data, and the CDOM data in a certain depth range is subjected to moving average according to the analysis requirement.

The data averaging specific procedure is as follows: firstly, processing the depth data of the CTD into delta m average data to obtain the starting time corresponding to each delta m; secondly, according to the starting time, finding the CDOM time sequence of the corresponding time period, and averaging the CDOM time sequence to obtain delta m average CDOM section data.

The invention provides a field CDOM data processing method measured by the CTD based on SUVF carried on the CTD, realizes the acquisition, conversion, quality control and averaging of CDOM data, fully considers the preparation work before observation, the temperature sensing before instrument placement, the interference factors appearing around a probe, the error caused by sampling frequency and the like, greatly shortens the time for processing the data, forms a standardized data processing flow, obviously improves the working efficiency, and provides the standardized field-observed CDOM data with processed errors for the subsequent analysis of the distribution characteristics of the CDOM in the ocean.

Drawings

FIG. 1 is a flow chart of a CDOM data processing method based on an ultraviolet fluorescence sensor mounted on a Sea-Bird 911plus CTD;

FIG. 2 CDOM data processing: (a) observing the change of the depth along with the time sequence, wherein the black bold line is intercepted data; (b) change in processed CDOM with depth.

Detailed Description

The invention provides a method for processing CDOM data measured by an ultraviolet fluorescence sensor based on the ultraviolet fluorescence sensor carried on a Sea-Bird 911plus Temperature salt Depth instrument (CTD). The method mainly processes the large-quantity original data with singular values into the data which are average and smooth in a certain depth range, and further forms a standard CDOM data flow for processing the data measured by the ultraviolet fluorescence sensor. And analyzing the processed data to know the space-time distribution characteristics of the CDOM in the ocean.

The technical scheme (figure 1) adopted by the invention is as follows:

1. data acquisition: before marine observation, firstly, the SUVF needs to be installed on a Sea-Bird 911plus CTD, secondly, the output variable of the CTD needs to be set, and finally, the CTD needs to be put into water for testing, so that the working state of an instrument is confirmed to be good, and the observation requirement is met. Sailing the ship to the appointed station position, guaranteeing to transfer the ship side windward of instrument, using the on-board arm slowly at the uniform velocity with the CTD shelf put in and withdraw, guarantee that data is effective and stable.

2. Data conversion: converting original data such as depth, temperature salt, CDOM and the like measured by an instrument into a cnv format which can be processed by Matlab by using professional software carried by the CTD;

3. and (3) data quality control: firstly, the CTD needs to sense temperature below the sea surface for 2 minutes before being released, so that the instrument starts to work, and the data needs to be deleted when being processed; second, errors due to sampling frequency may result in CDOM measurements that may have a 0 value, requiring that the 0 value be reassigned to nan when processing the data; thirdly, as bubbles or other factors may be influenced around the probe in the observation process, negative values may appear in the CDOM measurement values, and the negative values need to be reassigned to 0 when data is processed; fourth, during observation, the CDOM measurements may also suddenly exhibit abnormally high values, requiring de-peaking while processing the data. The peak is determined based on the multiple of the standard deviation, the local standard deviation of the first derivative and the derivative of the CDOM section in the corresponding time is firstly calculated, if the ratio of the two exceeds a certain set threshold value, the peak is determined to exist, and then the average value of the CDOM at the two ends of the peak is used for replacing. The principle formula is as follows:

where i is the data sequence of the CDOM profile, t_iTime of corresponding position, c_iCDOM data for corresponding locations measured for SUVF, S_iThe first derivative of CDOM with respect to time, STD is the standard deviation of the first derivative with respect to time of the data for the profile. If the absolute value of the first derivative of CDOM is greater than a certain multiple of the standard deviation of the first derivative, i.e. | S_i|>The CDOM data can be judged to have mutation along with time by multiplying alpha by STD, wherein alpha is a parameter. After deletion of the mutated CDOM data, the compensation was performed by linear difference.

4. Data averaging: the depth data on the CTD corresponds to the CDOM data one by one, and the CDOM data in a certain depth range can be subjected to moving average according to the analysis requirement, such as the interval of 0.2m, 0.5m, 1.0m and the like, so that the data can be conveniently subjected to in-depth analysis. The specific process is as follows: firstly, processing the depth data of the CTD into delta m average data to obtain the starting time corresponding to each delta m; secondly, according to the starting time, finding the CDOM time sequence of the corresponding time period, and averaging the CDOM time sequence to obtain delta m average CDOM section data.

The invention is further explained below by combining with the field observation data of 2019.

1. Data acquisition: before marine observation, the SUVF is firstly installed on the Sea-Bird 911plus CTD, the CDOM is added to an output variable of the CTD, and finally the CTD is put into water for testing, so that the working state of an instrument is confirmed to be good, and the observation requirement is met. The ship is driven to a preset station, the ship side windward side for lowering the instrument is guaranteed, the ship-borne mechanical arm is used for slowly throwing and withdrawing the CTD frame at a constant speed, and the data are guaranteed to be effective and stable.

2. Data conversion: converting original data such as depth, temperature salt, CDOM and the like measured by an instrument into a cnv format which can be processed by Matlab by using professional software carried by the CTD;

3. and (3) data quality control: firstly, deleting data in a temperature sensing stage, and selecting downlink data (fig. 2 a); second, the value of 0 of CDOM due to sampling frequency is reassigned to nan; thirdly, reassigning the negative value of CDOM to 0; fourth, de-spiking the protrusion that occurs in the CDOM measurement during observation. The peak is determined based on the multiple of the standard deviation, the local standard deviation of the first derivative and the derivative of the CDOM section in the corresponding time is firstly calculated, if the ratio of the two exceeds a certain set threshold value, the peak is determined to exist, and then the average value of the CDOM at the two ends of the peak is used for replacing.

4. Data averaging: the CDOM data at intervals of 2m are subjected to a moving average. The specific process is as follows: firstly, processing the depth data of the CTD into 2m average data to obtain the starting time corresponding to each 2 m; secondly, according to the starting time, finding the CDOM time sequence of the corresponding time period, and averaging the CDOM time sequence to obtain 2m average CDOM section data.