ncargf90: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/ncargf90 - from package: ncl-devel

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/ncargf90 - from package: libncarg-bin

You may install the required package with command apt-get install {package}

Error in other languages:
ncargf90: bevel nie gevind nie
ncargf90: comandă negăsită
ncargf90: comando não encontrado
ncargf90: commande introuvable
ncargf90: command not found
ncargf90: käsku ei ole
ncargf90: không tìm thấy lệnh
ncargf90: komanda nerasta
ncargf90: Kommando nicht gefunden.
ncargf90: kommandot finns inte
ncargf90: komut yok
ncargf90: nie znaleziono polecenia
ncargf90: níor aimsíodh an t-ordú
ncargf90: no se encontró la orden
ncargf90: no s'ha trobat l'ordre
ncargf90: opdracht niet gevonden
ncargf90: parancs nem található
ncargf90: perintah tidak ditemukan
ncargf90: príkaz nenájdený
ncargf90: příkaz nenalezen
ncargf90: команда не найдена
ncargf90: командата не е открита
ncargf90: 命令找不到
ncargf90: コマンドが見つかりません