Direct access

This approach to getting the data is preferable. It exploits the full capacity of the Data Access Protocol and avoids downloading huge amounts of data. You access one of the wave hindcasts inside your script, therefore your programming language of choice must have libraries that implement the Data Access Protocol.

• Ensure that an up-to-date version of Pydap, requests and lxml are installed:

pip install Pydap requests lxml

• To get direct access to each of the selected wave hindcast (ERA5-WW3, CFSR-WW3, MERRA2-WW3, ERAi-WW3), you need to connect to the server first. It can be accomplished by using setup_session from the pydap library. To get the file handler, use setup_session from the same library. So the final code will look like:

from pydap.client import open_url
from pydap.cas.get_cookies import setup_session

# connect to the NAAD database
session = setup_session("https://wave-hindcast.ocean.ru/accounts/login/",
        username="USER_NAME",
        password="USER_PASSWORD"
        )

# get the file handler
dataset = open_url('https://wave-hindcast.ocean.ru/dap/dapserver/CFSR-WW3/1980/cfsr_ww3_1980_hs.nc',
        session=session)

# read the variable
var = dataset['hs']

# print the array sizes
print(var.shape)

Download to a local machine

This way of obtaining the data may be more conventional but is not recommended because it is generally slow and takes a lot of storage on a user's machine. Nevertheless, two methods are available:

• web interface

To access the data you need to sign in to the WAVE-HINDCAST server. You will then be able to see the file structure and to download the wave hindcast data manually.

• wget

The example below downloads all files with SWH according to the CFSR-WW3 hindcast in the folder https://wave-hindcast.ocean.ru/dap/CFSR-WW3/. Don't forget to replace USER_NAME and USER_PASSWORD with your username and password.

#!/bin/bash
USERNAME="USER_NAME";
PASSWORD="USER_PASSWORD";
LOGIN_PAGE="https://wave-hindcast.ocean.ru/accounts/login/";
COOKIES_FILE="naadcookies.txt";
CSRF=`wget -qO- --keep-session-cookies --save-cookies $COOKIES_FILE $LOGIN_PAGE \
    | grep "csrfmiddlewaretoken"|sed -e's/.*name=\"//;s/value//;s/[\",\>,\ ]//g;'`;
wget -qO- --keep-session-cookies --load-cookies $COOKIES_FILE \
    --save-cookies $COOKIES_FILE  \
    --post-data "username=$USERNAME&password=$PASSWORD&$CSRF" \
    --referer $LOGIN_PAGE $LOGIN_PAGE
wget --keep-session-cookies --load-cookies $COOKIES_FILE \
    -r --no-parent https://wave-hindcast.ocean.ru/dap/CFSR-WW3/